In just a few short years in Washington, Sen. Ted Cruz has elbowed his way through the GOP ranks to become one of the party’s most vocal and polarizing members. The 44-year-old Texas Republican, who announced Monday morning that he is running for president in 2016, has been one President Barack Obama's severest critics and was a key player in the 2013 government shutdown.

Cruz was born in Canada to American parents but has since renounced his Canadian citizenship. He graduated from Princeton University with a B.A. in public policy in 1992 before earning his J.D. from Harvard Law School three years later. From 2003 to 2008, he served as solicitor general of Texas, becoming the youngest, first Hispanic and longest-serving solicitor general in the state's history.  

Cruz is the first person to officially declare his candidacy in the 2016 presidential elections. He enters a crowded filed that is likely to include Wisconsin Gov. Scott Walker and former Florida Gov. Jeb Bush, among others. Here’s where Cruz stands on the issues. 

Cruz on Obamacare

Cruz has long been one of Congress’ most vocal opponents of the Affordable Care Act, commonly known as Obamacare. In September 2013, he spoke for more than 21 hours against Obamacare in one of the longest Senate speeches of all time. “All across this country Americans are suffering because of Obamacare,” he said. “Obamacare isn't working. Yet fundamentally there are politicians in this body who are not listening to the people.”

That month, Cruz joined Republican Sens. Rand Paul of Kentucky and Mike Lee of Utah at an anti-Obamacare rally hosted by Tea Party groups.

During the government shutdown of October 2013, during which Republicans aimed to defund Obamacare, Cruz joined the senators opposing a bill that funded the government through Jan. 15, 2014.

Cruz has even compared Obamacare to the Nazis. “Look, we saw in Britain, Neville Chamberlain, who told the British people, ‘Accept the Nazis. Yes, they’ll dominate the continent of Europe, but that’s not our problem. Let’s appease them. Why? Because it can’t be done. We can’t possibly stand against them.'”

Cruz on immigration

Cruz voted for Senate Amendment 1197, which would have required 350 miles of fence along the U.S.-Mexico border to be completed. The Senate ultimately rejected the amendment.

Cruz criticized Obama’s executive action granting amnesty to millions of undocumented immigrants, saying the president overstepped his boundaries. “We should use the constitutional checks and balances that we have to rein in the abuse of power of the executive,” he said. Cruz has also supported giving law enforcement in Texas more power to ask people about their immigration status, and tripling the size of the Border Patrol.

Cruz on gun control

In April 2013, Cruz voted against banning high-capacity magazines of over 10 bullets, according to On The Issues. He also voted in favor of an absolute right to gun ownership, has argued against “burdensome” gun restrictions, and criticized Obama for supporting the 2013 United Nations’ Arms Trade Treaty, which regulates the international weapons’ trade.

"When it came time for a vote [on gun control], every single proposal of the president’s that would have undermined the Second Amendment was voted down,” Cruz said of Obama’s gun-control package following the Newtown shootings in 2012, during an October 2013 speech at Iowa’s Reagan Dinner. “That was the power of the grass roots.”

Cruz on global warming

Cruz has said he is skeptical of climate change science and has dismissed data that documents the melting of the Arctic. "Other parts are going up,” Cruz argued to CNN in February 2014. “It is not - you know, you always have to be worried about something that is considered a so-called scientific theory that fits every scenario. Climate change, as they have defined it, can never be disproved, because whether it gets hotter or whether it gets colder, whatever happens, they'll say, well, it's changing, so it proves our theory.”

He added: "The last 15 years, there has been no recorded warming. Contrary to all the theories that – that they are expounding, there should have been warming over the last 15 years. It hasn't happened.”

Cruz on ISIS

Cruz has criticized the White House for not taking the threat of ISIS, also called the Islamic State, seriously enough, and suggested bombing the terrorist group “back to the Stone Age.”

“First and foremost, Washington should resolve to make border security a top priority finally, rather than an afterthought, of this plan in light of concerns about potential ISIS activities on our southern border,” Cruz wrote last year. He also chastised Obama in the wake of the beheading of two U.S. journalists in September for not seeking Congress’ approval before taking action.

He added that “if the threat is imminent, we need more urgency and seriousness out of our commander-in-chief.”