Of all the issues likely to surface at Wednesday night's Republican debate in Mesa, Ariz., immigration is a fairly safe bet.

That's because Arizona has come to embody the GOP's approach to immigration, in 2010 passing a highly controversial law that became the model for similar bills passed by Republican-controlled legislatures in Georgia, Alabama, South Carolina and Utah.

In addition to mandating new penalties for employers who hire undocumented immigrants, Arizona's law provoked an outcry for empowering police officers to check the immigration status of people they suspect of being in the country illegally. Under that mechanism, routine traffic stops could result in deportation.

Arizona Law: Approaching Republican Party Doctrine Status

Critics of the law denounced it as discriminatory and unnecessarily harsh, but its enforcement-first approach has approached the status of Republican party doctrine. Alabama followed Arizona's lead but took it a step further: as originally written, the Alabama law would have prohibited anyone -- including religious institutions -- from sheltering or harboring undocumented immigrants, compelled schools to ask students about their immigration status and required police officers to check the status of those they detain.

Such measures seem inhumane to detractors, but Mitt Romney has embraced them wholeheartedly. Romney's description of his immigration policy as self-deportation was widely mocked, but he was essentially articulating the premise of the new laws for which Arizona provided a template: If life becomes difficult enough for undocumented immigrants, they will leave. Romney has also campaigned with Kris Kobach, the Kansas secretary of state who helped write the Arizona and Alabama laws.

The federal Justice Department criticized enforcement-at-all-costs approach in a lawsuit seeking to block parts of the Alabama law. The Obama administration has also sued Arizona, Utah and South Carolina over their respective immigration laws, contending that they are improperly trying to supplant the federal government's sole authority to enforce immigration law.

States have strenuously objected that the federal government is interfering in their affairs. That clash helped explain the much-publicized runway confrontation between Arizona Gov. Jan Brewer and President Barack Obama, in which Brewer appeared to thrust an accusatory finger in Obama's face. Brewer has denounced the Obama administration's attempts to block the Arizona immigration law.

As a direct result of failed and inconsistent federal enforcement, Arizona is under attack from violent Mexican drug and immigrant smuggling cartels, Brewer said in a July 2010 press release after the Department of Justice sued her state. Now, Arizona is under attack in federal court from President Obama and his Department of Justice.

Another Chance for GOP Candidates to Rebuke Federal Government

Attacking an expansive role for the federal government has been a dominant theme of the Republican primary thus far, with candidates taking every opportunity to denounce the health care overhaul and the Dodd-Frank financial reform bill as examples of the Obama administration's overreach. At Wednesday night's debate, that could come up in the context of Arizona and the administration clashing over immigration.

Immigration has proved to be a combustible topic throughout the 2012 Republican presidential campaign, with candidates scrambling to prove their conservative bona fides. Texas Gov. Rick Perry was attacked on all sides for defending a bill that gave in-state tuition to undocumented immigrant students in Texas, contributing to the Perry campaign's demise.

Rick Santorum, who said the in-state tuition policy was an attempt to attract the illegal vote -- I mean, the Latino voters, spent Tuesday courting Arizona immigration hardliners. He held a luncheon with recently recalled state Sen. Russell Pearce, a driving force behind the immigration law, and Maricopa County Sheriff Joe Arpaio, the self-proclaimed America's toughest sheriff whose office was found to have committed a wide range of civil rights violations against Latinos.