Such a candidate isn’t necessarily an obvious favorite in Iowa or the other caucus states but a mainline conservative with strong credentials on cultural issues and who can speak the language of the religious right could win Iowa. And after Iowa, you’d rather be a mainline conservative than a tea partier. New Hampshire, Florida, Michigan, and potentially South Carolina (if the religious right is satisfied on cultural issues), would all prefer a mainline conservative to a Tea Party candidate. History makes it clear that mainline Republicans tend to win the nomination.
So Marco Rubio’s positioning isn’t so bad. Immigration might weaken his appeal with a few Republicans, but it doesn’t look like it was a death blow. Rubio’s unfavorables aren’t very high, and John McCain came back from worse. And doing the bidding of the business-wing of the GOP is generally a pretty good idea—it’s probably the most important wing of the “invisible primary,” worth plenty of fundraising dollars. Conversely, Rubio’s stock would have taken a hit if he didn’t help advance immigration reform. It’s unclear whether Rubio ought to have taken a lead on immigration reform, especially in retrospect, but Rubio still has relatively broad appeal within the party.