Did Romney lose because of immigration? Find out. (Hispanic vote, Obama wins)
While Obama might have picked up a good share of the "Hispanic vote", he was always going to get a large share of Hispanics voting for him.
On the immigration topic, what hurt Romney was that he didn't use it correctly. Instead of Hispandering - a failed strategy that just helps the Democrats - Romney should have shown how Obama is wrong on immigration. That would have been incredibly easy for him to do; for instance, the DREAM Act is an openly anti-American bill that would (depending on the version) allow foreign citizens to deprive U.S. citizens of college educations and that would let former illegal aliens drive struggling Americans out of work. Instead of opposing the DREAM Act, Romney validated its concepts.
Expect illegal immigration supporters - that is, virtually the entire establishment - to try to blame Romney's loss in part on him being "strong" on immigration. That does not reflect reality.
The problem with Romney is that he was too weak on immigration and - instead of using the issue to undercut Obama - he validated the corrupt, anti-American concepts of the leaders of the Democratic Party.
See Mitt Romney for a timeline of how Romney hurt himself by going weak on immigration, and see Obama immigration for all the many ways a smarter, less corrupt Romney could have used the issue to undercut Obama with his base.