“He’s stuck between two lanes with his blinker on,” said one party strategist with ties to a competing campaign.

Ideologically, Rubio’s allies contend he maintains broad appeal among conservative and moderate Republicans alike. But some of his recent policy maneuvers appear to have positioned him more within the establishment segment of the GOP — a space already crowded with Bush, Kasich, and Christie.

In the aftermath of the Supreme Court decision on gay marriage, Rubio did not call for a constitutional amendment to define marriage, as did many candidates who are courting conservatives. On immigration reform, he said recently that he would be open to a path to citizenship for undocumented immigrants, a position that is untenable with many conservative voters.

“I don’t think they’ve come to grips yet with the fact that this has pushed them into the establishment lane,” said a Republican operative working for a competing campaign. “He’s still trying to be all things to all people.”