That's produced a familiar fault line which is laid bare nowhere more starkly than in the immigration debate. The pro-reform side tends to be nationally oriented Republicans, those who are worried about ensuring the party has broad appeal in a diverse country. They occupy the strategist ranks (see Karl Rove, for example) and, in many cases, U.S. Senate seats. It's no accident that the bipartisan proposal originated in the Senate. On the other side are people with more parochial interests, whether avoiding primaries in their heavily gerrymandered districts or rousing the rabble for talk radio ratings.
Trying to uncomfortably straddle the middle are the would-be presidential class of 2016. So Rubio pushes inexorably forward on the issue all the while trying to give very high profile voice to conservative concerns. Further to his right Kentucky Sen. Rand Paul, who has ostensibly embraced some form of reform, called for the whole process to slow down because of the Boston attacks.
Pace is critical. Enemies of reform reportedly plan to kill it by grinding it to a halt. Which brings us back to Boehner. Immigration reform could well come down to the question of whether he values his national party's interests over his House colleagues' hard-line desires.
My bet is Boehner saves the GOP from itself and lets a reform bill pass.