Why Rubio is most likely Republican nominee

Marco Rubio is the most likely candidate to win the Republican 2016 presidential nomination.

I said early on that Rubio was in a first tier of contenders with Jeb Bush and, before he dropped out, Scott Walker. There was a solid case for and against each of them. Well, the case against Walker turned out to be correct, while the one for Rubio has looked stronger and stronger.

Ross Douthat of the New York Times recently described Rubio's oddly intangible front-runner status. After good reviews for his debate performance (and terrible ones for Bush), that has changed. Rubio has picked up his first two endorsements from his fellow U.S. senators -- Colorado's Cory Gardner on Monday and Montana's Steve Daines on Tuesday. After getting off to a slow start in high-visibility endorsements, Rubio has been on a roll for a while now. He has nailed down seven members of the House since Sept. 21. Over the same period, the other 14 GOP candidates had 10 new House endorsements combined.

This shift to Rubio is happening at other levels, too. Last Tuesday, I counted 67 state legislators in Rubio's column; a short week later that number was reported to be up to 80.

He still trails Bush in total endorsements. But remember the 2008 Democratic contest. Hillary Clinton's strong party connections allowed her to take an early but not decisive lead among party actors, and then Barack Obama spent the fall of 2007 beginning to catch up. And Bush's early lead has been far less impressive than Clinton's was then. A lot more free-agent party actors remain available and could wind up with Rubio.

That's even more likely to happen if Rubio's debate performance last week winds up producing even a modest polling surge. We have yet to see a national poll taken entirely after Wednesday's debate, but state surveys hint that Rubio could emerge in a solid third place -- and therefore in position as an alternative to current polling leaders Donald Trump and Ben Carson. Rubio's main strength remains that he can appeal to almost every Republican group.

Not that he has it wrapped up. Other candidates have had good stretches but eventually faded. Nor has he faced the pressures of being a front-runner, scrutiny that has taken down plenty of previous candidates. There's no evidence -- yet -- that he's won over the bulk of the party, just increasingly strong hints that it's happening. And of course even if the party falls in line for him, that will have to translate into votes in party primaries and caucuses, Trump and Carson notwithstanding.

I don't think his record on immigration will derail his chances, just as I never thought Mitt Romney's health-care record would keep him from getting the Republican nomination in 2012. Rubio has already repudiated his Senate bill that offered a path to citizenship for undocumented immigrants in the U.S. He'll most likely say whatever anti-immigration Republicans want to hear, and that should be enough.

We still have a long way to go until the caucuses in Iowa on Feb. 1, let alone to the Republican nomination. The first tier is still Rubio and Bush. But they're no longer on equal footing. Rubio leads.

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Jonathan Bernstein, a politicial scientist and author, is a Bloomberg View columnist.

Previously:

• 10/28/15: Boehner tries to give Ryan a clean slate
• 10/26/15: What Carson's Iowa surge doesn't mean
• 10/21/15: Seriously, Trump will not become president
• 10/19/15: Political parties are changing, not dying
• 08/17/15: Trump's bid could end in one of three ways
• 08/04/15: Joe Biden boomlet is over before it starts
• 08/03/15: How to know when John Boehner is in trouble
• 07/14/15: Scott Walker tests tea party's seriousness
• 07/01/15: Chris Christie, king of the 2016 long shots
• 06/23/15: The next step if Obamacare loses in court
• 06/16/15: Jeb Bush and the Endless Campaign
• 06/15/15: Jeb Bush won't win if he's the safe choice
• 06/04/15: Why candidates are snubbing Iowa Straw Poll
• 06/03/15: Graham tests his luck in Republican primary
• 06/01/15: George Pataki has a pro-choice problem
• 05/28/15: Republicans may be forced to save Obamacare
• 05/06/15: Mike Huckabee will make history, win or lose
• 05/05/15: Why Hillary needs Sanders
• 02/25/15: Scott Walker isn't ceding party cash to Bush
• 02/23/15: How the Kochs wasted a fortune on campaigns
• 02/16/15: Why candidates can lie, but reporters can't
• 02/09/15: Don't mess with . . . Iowa --- as first caucus state
• 02/06/15: Biggest threat to Rand Paul in 2016?
• 02/04/15: Christie's measles vaccine madness explained
• 02/02/15: Two takeaways from Romney's latest
• 01/20/15: Ernst draws short straw with Obama response
• 01/16/15: Romney is the only one who thinks he's Reagan
• 01/13/15: How GOP underdogs could very well take on their establishment