The only Republican candidate who has won the nomination in the past 40 years without clear party support was McCain in 2008. In that year, however, there was no favorite, and McCain clearly tried to make good with the GOP grandees, after his 2000 bid. In the end, it worked. After the first two primaries, McCain became the establishment candidate.
Rubio’s push on immigration reform is going to get him some insider credit. Faith and Freedom Coalition President Ralph Reed looks favorably upon Rubio’s push. Most donors like Rubio’s new role. He’s also bound to win plaudits from the GOP establishment in the Senate, which is pushing for immigration reform. Overall, this is definitely the correct move for a person who might otherwise be seen as too “outsidery”.
Immigration reform has the additional advantage of being seen as a moderating force. It’s backed by most Americans and is generally supported by the party establishment because it’s seen (rightly or wrongly) as an electoral winner…
So, I think Rubio is making a smart political play by supporting immigration reform so openly. It’s the type of issue that will garner him plaudits from the party establishment – which generally gets to pick Republican nominees. It’ll help to reassure Republicans that he can win, which will likely be a chief concern for primary voters in 2016, as it was in 2012.