>> There is no particular political affinity between, say, Cuban-Americans and Mexican-Americans. <<
Sure. But I remember back in 2007 and 2008, when many “experts” were saying that Obama wouldn’t have a strong appeal to most Afro-Americans, since he didn’t have “slave blood” and since he grew up in Hawaii rather than in the ghetto. How wrong they were!
Therefore, I have to wonder if the same sort of “racial pride” might not influence a big percentage of Mexican-American voters. A useful impact wouldn’t even require an actual majority. So if for example Rubio could draw in something like 30 to 40% of the Mex-Am voters, then they might give the GOP the margin of victory in a few swing states like NM, NV and CO.
(And it probably need not be said that with a close tally in the electoral college, these states could determine the outcome of the POTUS contest.)
A Romney-Rubio ticket may well draw 30-40% of Mex-Am voters.
But it won't do it out of "racial pride". That's not the kind of thing that moves conservatively inclined Hispanic voters.
Please dissuade yourself of the notion that Hispanic voters are akin to black voters.