What forces are preventing the issue of immigration from being resolved?

In an article from a respected magazine, The Economist, a caption reads, "Tight legal controls have driven Latinos to illegality. Why not try reversing the policy? Politics, that's why." After reviewing various other sources, it becomes apparent that American politics are, in fact, the only major obstacle that stands in the way of resolving the debate over immigration.
The Economist contends that, "The difficulty is to reconcile economic reality with political reality." Although immigrants are proven to be beneficial to the United States' economy, immigration is a tough issue to tackle for both Republicans and Democrats. Many politicians are afraid of negative repercussions because of their "soft" views. The Economist briefly describes President Bush's 2004 proposal for a guest-worker program, and then goes on to say, "Republican politicians, with their eyes on [the 2006] midterm elections, openly defy their president." Immigration was a major issue in Tom Daschle's senatorial run; political analysts blame his defeat on his liberal views on immigration. After California Republican Congressman David Drier saw his support weaken due to his "soft" views, he toughened up, sponsoring legislation that, if enacted, would impose penalties on employers for hiring illegal aliens. However, a counter force to this hard-line view exists. Big businesses employ many of the eight to ten million illegal immigrants in the US. The Economist notes that "few politicians want to alarm the very businessmen who finance their election campaigns" by enacting legislation that would penalize employers for giving jobs to illegal aliens. An article from the McClatchy-Tribune News Service describes how John McCain, a Republican presidential candidate, almost lost the South Carolina primary due to his bipartisan immigration reform plan. Fellow Republican Lindsey Graham defended McCain, and was shouted down by his voters. Although McCain still pulled of a victory because of his positions on other issues, "most agree McCain's stance on immigration has cost him some support."
With such forces acting upon our politicians, it is a wonder immigration reform has gotten anywhere at all. Because views vary from "The libertarian advocacy of open borders to the isolationist instinct to fence them off," government leaders are being pulled in two different directions and unable to accomplish anything.