A few months after the acrimonious debt ceiling skirmish last summer, an ordeal that seemed to signal a new nadir for the spirit of compromise in Washington, President Obama unveiled a new mantra.

We can't wait for an increasingly dysfunctional Congress to do its job, Obama told a Nevada audience in late October. Where they won't act, I will.

We can't wait was a reversal of the president's previous exhortation to pass this bill, a phrase he had repeated in speech after speech as he stumped across the country fruitlessly imploring Congress to vote on a $447 billion jobs bill. The phrase began crowning press releases announcing a series of executive orders aimed at helping veterans find jobs, or creating a Consumer Privacy Bill of Rights, or launching research pilot programs.

Last week's announcement that the administration would shield many young undocumented immigrants from being deported was a different order of magnitude. The order could allow hundreds of thousands of young immigrants to avoid deportation and find legal work, and the shift has already sent tremors through the presidential race.

It also looks strikingly similar to the DREAM Act. The Obama administration's new directive addresses a similar group of people -- immigrants who were brought to the country illegally as children, have stayed out of trouble, and have pursued school or military service - and while it does not open a path to citizenship, as the DREAM Act would, it promises to free many young immigrants from the fear of deportation.

The Republican backlash was predictably swift. Rep. David Schweikert of Arizona introduced a bill that would strip the president of his authority to spare some immigrants from deportation, and Rep. Steve King of Iowa threatened to sue.

President Obama's actions will violate the constitutional separation of powers and at least two federal laws, King said in a statement, adding that lawsuit concerned the constitution and the rule of law.

By that logic, many of Obama's predecessors were also scofflaws. It is part of a pattern that presidents have for some time been exercising these unilateral powers to effect changes in policy domains where Congress is gridlocked, said William Howell, a professor of political science at the University of Chicago.

Indeed, President Franklin Roosevelt issued an executive order known as the Fair Employment Act, prohibiting racial discrimination in the defense industry, and President Truman bolstered that effort by invoking his executive authority to begin desegregating the military. President Reagan provoked a controversy when he allowed Bob Jones University to keep its tax-exempt status despite the Internal Revenue Service's finding that the school was ineligible because it advanced racial discrimination. And President George W. Bush blocked stem cell research, while also making it easier for faith-based groups to get federal funding.

The new immigration policy is not the first time Obama has found a way to implement key pieces of his policy agenda without Congress. On two other prominent issues, same-sex marriage and education, the president has registered significant accomplishments without lawmakers casting a vote. The legal justification for each of the three is different, but the premise is the same: we can't wait.

Gay Marriage

The bruising debt-ceiling battle was still months away when President Obama instructed his Department of Justice, in February of 2011, to stop defending the Defense of Marriage Act. The law prohibits the federal government from recognizing same-sex unions, which means that couples who are legally wed in states that recognize gay marriage are still barred from an array of benefits that include joint health insurance and the ability to sponsor one's spouse for a green card.

Foreshadowing Obama's public endorsement in May of same-sex marriage, Attorney General Eric Holder wrote to Speaker of the House John Boehner explaining how Obama had determined that the Defense of Marriage Act violates the equal protection component of the Fifth Amendment. As a result, the administration would no longer be defending the law in court.

The responsibility for passing marriage laws falls to the states, where advocates are trying to advance same-sex marriage in a slow, state by state marathon. But the administration's refusing to argue for the Defense of Marriage Act in court -- in effect, calling it unconstitutional -- was a significant victory for gay rights advocates, as well as a clear signal of where Obama stood.

Republicans immediately condemned the president. Rep. Lamar Smith of Texas, chair of the House Judiciary Committee, warned of letting the personal views of the president override the law of the land, and Boehner convened a legal advisory group to defend the law.

The constitutionality of this law should be determined by the courts -- not by the president unilaterally -- and this action by the House will ensure the matter is addressed in a manner consistent with our Constitution, Boehner said in a statement. The legal team is currently planning to ask the Supreme Court to rule on a DOMA challenge wending its way through federal courts.

Despite criticisms that Obama is refusing to carry out a duly enacted law, there is ample precedent for presidents doing just that. Thomas Jefferson rejected the Alien and Sedition Acts, for instance, believing they violated the 1st amendment. In a 1994 memo, then-assistant Attorney General Walter Dellinger described the situations in which a president may appropriately decline to enforce a statute that he views as unconstitutional.

We do not believe that a President is limited to choosing between vetoing, for example, the Defense Appropriations Act and executing an unconstitutional provision in it, Dellinger wrote. In our view, the President has the authority to sign legislation containing desirable elements while refusing to execute a constitutionally defective provision.

Education

No Child Left Behind was not working. President Bush's education overhaul passed in 2001 with bipartisan support, and by 2011 there was something approaching a bipartisan consensus that the law had failed. No Child Left Behind tried to increase accountability and improve school quality by requiring schools to demonstrate steadily rising test scores. Schools that did not hit their yearly targets faced punishments that could include mass firings.

In June of 2011, Education Secretary Arne Duncan warned that the country was hurtling towards a slow-motion education train wreck. No Child Left Behind required that 100 percent of students register proficient scores on reading and math tests by 2014, a goal that was widely seen as ludicrously unattainable. Unless Congress amended the law, Duncan said, the administration would act.

And act it did. Obama ultimately announced that he was offering states waivers exempting them from the 2014 proficiency requirement. In exchange for those waivers, states would need to submit proposals for how they would initiate a number of education reforms the administration favored, from writing new college and career readiness standards to crafting systems to measure how well teachers were performing.

To many education experts, it was a stunning move. Without the consent of Congress, the administration had simultaneously dismantled a central piece of existing education law and found a way to have states adopt a new set of education policies.

It is unparalleled in terms of what we have seen before, said Grover Whitehurst, an education policy expert at the Brookings Institution who worked for the Department of Education during the Bush administration.

In order to free states from the testing mandate, Duncan invoked a section of No Child Left Behind that enables the education secretary to waive parts of the law if states request it. Margaret Spellings, who was education secretary under President Bush, used that authority to enroll states in a pilot program that gave them more leeway in deciding how to treat struggling schools.

But the Obama administration's move was far bolder, Whitehurst said -- rather than pursuing innovations at the margin, as past secretaries had, Duncan used the waiver to completely rewrite the law.

While some members of Congress professed outrage, the overall reaction to the school waivers was muted. The fact that that particular slice of No Child Left Behind was widely unpopular gave Obama the political cover he needed.

There was a calculation that Republican state leaders would want this relief just as much as Democratic state leaders and that would undercut the ability of Congress to hold them to task for usurping congressional authority, Whitehurst said.

Immigration

Congress passes the laws, and the executive branch executes them. That is the premise underlying the administration's extraordinary decision to stop deporting immigrants who would otherwise qualify for removal. Because immigration enforcement is a federal prerogative, the president can guide how it is carried out.

This is well within the mainstream of a normal exercise of presidential powers as they have been used in this century, said Eric M. Freedman, a constitutional law expert at Hofstra University Law School. There is nothing inappropriate about deciding to exercise enforcement discretion with respect to the laws. All enforcement agencies do that, all the time.

After President Bush's push for comprehensive immigration reform collapsed, for example, administration officials detailed a 26-point plan laying out what they could do within the context of the existing statutes. Some of the measures tightened workplace enforcement, while others reformed worker visa programs.

Until the laws change, we are enforcing the laws as they are to the utmost of our ability using every tool that we have in the tool box, and we're going to sharpen some of those tools, Homeland Security Secretary Michael Chertoff said at the time.

The decision to halt deportations of DREAM-eligible immigrants builds on the Obama administration's previous efforts to recalibrate immigration enforcement. Noting that immigration personnel have limited time and resources, the administration released guidelines last summer dictating how field agents, immigration attorneys and judges should use their prosecutorial discretion in deciding which cases to pursue.

Immigrants with criminal records or who had repeatedly broken immigration laws were to be targeted. Those who had committed no crimes, had strong family ties or had pursued military service could be eligible to have their deportation cases suspended. The latter category would also include many of the DREAMers covered under the new directive.

What he's doing in this particular case is in a long line of prosecutorial discretion and other interim measures that many presidents going back as far as Eisenhower have done, Hiroshi Motomura, a law professor and immigration expert at the University of California, Los Angeles, said of the sweeping new order. I don't see this as doing anything out of line or particularly unusual.

Motomura said that the order offers only a bare-boned type of protection and does not claim the authority to extend permanent legal status or citizenship, something only Congress can do. But others think the new policy could have far greater repercussions.

President Obama is not simply offering an alternative interpretation as was done with past signing statements. He is stating categorically that he will not enforce a significant federal law, and he is also taking that step after Congress has repeatedly refused to pass this very proposal, said Jonathan Turley, a constitutional law expert at George Washington University.

Liberals may find that a future president wants to simply negate environmental provisions or provisions dealing with the separation of church and state, and they will be in a hard position, Turley added.

Future Repercussions

Turley's point echoes criticisms of the ways in which the Obama administration has gotten things done. The unifying concern is that Obama is setting a dangerous precedent for future chief executives who will not feel encumbered by Congress.

But to many scholars, Obama's actions are an inevitable outgrowth of the perpetual clash between the different branches of government.

The branches were deliberately set up to be in a power struggle with each other, and when one has the strength to impose its will that branch will do it, Freedman said. The disposition to grab as much power as the branch can get away with is built into the system.

Presidents are judged by what they have accomplished, regardless of the extent of Congressional opposition they face. When Americans vote for a particular presidential candidate, they are endorsing that candidate's ability to carry out a promised agenda.

It's the right of the executive branch to have a certain policy and to interpret the laws in the general way it believes is correct, so you would expect a Democratic administration to interpret the laws regarding, say, clean air, more seriously than a Republican one, said Harvey Mansfield, a professor of government at Harvard University. That's why you vote for one party's president over another. I don't think the executive should just be carrying out, in an errand boy sense, the legislative will.

That imperative may be stronger in an era marked by intense, often paralyzing partisanship in Congress. Thomas Mann, a congressional scholar at the Brookings Institution who recently completed a book on the topic, said Obama had few options outside of flexing his executive muscle.

Obama's increasing use of executive authority is an inevitable consequence of the unified, relentless opposition he has faced from Republicans in Congress from the beginning of his administration, Mann wrote in an email. With Republicans controlling the House and unwilling to compromise on anything of consequence, he has no alternative. The list of initiatives he has taken is growing long -- and it will get longer before the election.

That may be true. But it raises the risk of a self-sustaining pattern, one in which the two parties become more deeply entrenched in their ideological positions and the president, as a result, becomes more assertive.

There's a possibility here for a vicious cycle, said Michael Gerhardt, a constitutional law professor at the University of North Carolina, Chapel Hill. And unless or until Congress is able to act consistently and address these issues on its own, it makes it easier for the president to act unilaterally or act based on statutes that Congress has not yet revised.

There is one enduring check on presidential power: the electorate. But even at the ballot booth, worries about expanding presidential power confront the effects of new policies, even if they were enacted without Congress. It is a question of whether, to voters, the ends justify the means.

The Obama administration's new immigration order is a good example. Conservative voters could rebuke the president for overreaching and offering what they consider to be an amnesty to lawbreakers. But that could be offset by an energized Latino electorate motivated by the fact that Obama is finally keeping his long-deferred campaign promises.

I think voters will probably align themselves depending on the direction with which he's going, Gerhardt said. Some voters might be turned off by what they consider his consolidation of power, but I would hasten to add that a Republican president might do the same thing.