This includes most Democrats and perhaps a handful of Republicans. They want reform on the merits—having an undocumented underclass is bad policy—and on the politics. For Democrats, it's catering to a priority of one of their most important (and growing) constituencies (not just Latinos, but Asians as well), and for Republicans, it's the realization that they won't win another national election (or a personal one) unless they can eat into Latino support for Democrats.
The problem for Republicans in this camp is that their efforts are a long play—Latinos won't be switching their votes by 2016. But their party's future prospects won't improve until Latinos start doing so. Eventually.
The fake reformers
These are people who think that they can improve with Latinos by changing their "tone" and pretending to seek reform. These include people like Sen. Marco Rubio, who propose a path to citizenship, but only after the GOP certifies the border as "secure". As you well know, they'll never do that, so that 13 million new, heavily Democratic voters never enter the voter pool. They seek to create a legal limbo, where undocumented immigrants aren't rounded up and deported, but are still denied the rights of citizenship.
The bulk of the GOP considers the fake reformers sellouts, as even the mildest reforms are "reward" for "lawbreakers". They cling to the fantasy of mass deportations and the notion that 1) you can sweep our nation clear of the undocumented, and 2) that our nation could function without that source of cheap labor.
Democrats are mostly united behind genuine reform, though they include a smattering of xenophobes like Montana Sen. Jon Tester. Republicans, on the other hand, are divided between those who want half-measures, hoping it's enough to arrest their decline among Latinos, and the angry white male xenophobes who dominate their grassroots (and the House GOP caucus).
You can lend your voice to this debate by signing this Daily Kos/Worker's Voice petition thanking President Barack Obama for his call for comprehensive reform.