Along with many other Republicans, Paul Ryan has adopted a firm anti-amnesty, enforcement-first stance on immigration in recent years. But Ryan hasn't always held such a hard line: In the past, he has supported multiple bills that would have allowed some illegal immigrants to apply for temporary guest-worker status — including one bill that would have provided a pathway to a green card for certain illegal immigrant farm workers.

Immigration hasn't been a major policy focus for Ryan, but his evolution on the issue has largely mirrored his party's. Throughout the Bush administration, he supported bills that allowed certain illegal immigrants — primarily agricultural workers — to apply for temporary resident status. In 2005, he co-sponsored a bill introduced by Rep. Chris Cannon (R-Utah) that would allow qualified illegal immigrant farm workers to receive "temporary resident status and subsequently lawful permanent resident status" — i.e., a green card — if they met certain work and residency requirements. As recently as 2009, he co-sponsored a modified version of the same "AgJobs" legislation that would have given temporary worker status to certain illegal immigration farm workers, although without the same pathway to a green card.

Outside of guest farm workers, however, Ryan has largely taken a more aggressive stance. In late 2005, Ryan also voted for Rep. James Sensenbrenner's highly controversial bill that would have made illegal presence a criminal act (it's currently a civil offense) and turn smuggling and illegal entry offenses into aggravated felonies. In both the Bush and Obama years, he also repeatedly supported efforts to ramp up border security.

Ryan has since turned against any pathway toward permanent legal status. He still wants to expand visas for temporary and seasonal workers, citing his home state Wisconsin's reliance on such labor for agricultural work. But he says that he opposes visas that "would have allowed an illegal immigrant to stay in America indefinitely," he says on his congressional Web site. "They serve the same purpose as acquiring a green card, without having to leave the country or waiting at the end of the line. In my opinion, this approach amounts to amnesty."

Ryan has also voted against the DREAM Act to provide a legal pathway for illegal immigrant students, and he wants to implement a nationwide employment verification system to allow employers to check a potential worker's immigration status. That's been enough to persuade those who want to deter more immigration that Ryan is sufficiently hawkish on the issue. "In this past Congress, he's been a good deal better on immigration," says Mark Krikorian, executive director of the Center for Immigration Studies. "I'm reasonably encouraged by his evolution."

So there isn't much daylight between Ryan's current position on immigration and Romney's hardline stance. Romney has toughened his own stance on illegal immigration, attacking Newt Gingrich during the primary campaign for supporting some kind of permanent legal status for illegal immigrants. Romney has previously suggested that some illegal immigrants might be able to receive guest-worker status, as he indicated during his 2008 run. But he's built his immigration platform around "turning off the magnets of amnesty." And given Ryan's own hawkish turn, it's not unlikely that Romney's running mate will say much on the trail to contradict him.