share: digg facebook twitter Illegal immigration has emerged as a defining issue with remarkable staying power in a GOP presidential race that was expected to be primarily focused on the nation's struggling economy. The heated clashes over illegal immigration between the two Republican presidential rivals in this week's debate made clear the issue isn't going away. At every turn, Perry, the Texas governor, has been forced to defend his signing of a law that allowed some illegal immigrants to get in-state college tuition. [...] in some ways, immigration has shaped the increasingly bitter Republican nomination fight more than any other issue, particularly in a crowded field where the conservative candidates have more in common than not. [...] while conservative voters may be driving immigration chatter on the campaign trail, the candidates are stoking voter passions when given the opportunity. The outspoken Texan raised new questions at the debate about Romney's use of a landscaping company that employed illegal immigrants at his suburban Boston home several years ago. Polling suggests the issue may help the candidates score political points with Republican primary voters but could alienate the ballooning Hispanic population or hurt the candidates among independents in a general election matchup against President Barack Obama.