This look at Florida Sen. Marco Rubio's chances and path to win the Republican presidential nomination is part of a series here on The Fix looking at all the top candidates. To see the others, click here.
Where does he stand in the polls?
There's an old joke from horse racing about Secretariat being in first place, daylight placing second and the next horse in third. That's where Rubio is right now: In fourth place nationally behind Donald Trump, Ted Cruz and a lot of daylight.
Rubio's been running an odd campaign, focused more on his national presence than in any of the early states. He's visited Iowa far less than many of his competitors, for example, which runs contrary to how campaigns have been won in the past.
Perhaps because of that, his polling in Iowa and New Hampshire hasmirrored his national polling much more closely than other candidates -- which, at this point, is helpful. With the strength of the outsider candidates in the Republican field and the collapse of Jeb Bush, Rubio has been able to consolidate more support from those looking for a non-Donald-Trump candidate. Right now, for example, he's in third in Iowa and climbing.
How has he performed?
Fine. He's capable, compelling, a decent campaigner and a pretty good debater, and his TV spots have been generally good.
But political watchers would be excused for expecting more. The candidate whose watchword is his youth and vitality has not brought a lot of that to the trail.
What are his strengths?
Rubio's main strength is that he is a candidate who is more than palatable to moderate and establishment Republicans while not being unacceptable to the conservative base. There hasn't been much oxygen for anyone besides Trump so far, and less still for anyone unwilling to try to push politics-as-usual in front of a bus.
Simply appearing to be the main contender for the moderate vote -- slipping past Jeb Bush's awkwardness and John Kasich's anonymity -- may end up being hugely advantageous if the race comes down to one candidate who's an outsider and one who isn't.
What's more, he has a compelling life story and the ability to tell it. He's naturally likable in the way that Bush, for example, isn't. That's not the most important criterion for being president, but it's an important one forrunningfor the job.
What are his weaknesses?
Rubio doesn't seem to be running very hard. While most people probably don't care much that he's missed a large number of Senate votes as he's been campaigning, Rubio's campaign has also been criticized for its relative nonchalance. This may be a gamble that early-state visits don't mean much, which -- given that Rick Santorum has barnstormed Iowa and earned a spot at the bottom of the polls -- may be correct.
Part of that may be that his campaign is not raising as much money as many of his competitors. In the third quarter of 2015, he raised $5.7 million -- to Ted Cruz's $12.2 million, Bush's $13.3 million and Ben Carson's $20.8 million.
It's also hard to gauge the extent to which his involvement in the 2013 comprehensive immigration reform package will be a liability. Immigration has been central to the 2016 debate, thanks to Donald Trump's bear hug of it. Rubio has been hit on it repeatedly, but it could become more of a problem as the race narrows.
What would it take for him to win the nomination?
Rubio's best bet is to wait out the winnowing of the field, to be the last acceptable candidate standing in the rubble of the Republican establishment. If he remains viable as other more moderate candidates like Bush and Kasich drop out, he could conceivably consolidate their support -- perhaps even benefiting from Trump and Cruz splitting the anti-establishment vote as the race slogs on.
But at this point, adding up Rubio's, Bush's, Chris Christie's and John Kasich's national support gets you 27 percent -- still nine points behind Donald Trump and less than half of Trump and Cruz combined.
His campaign is talking about gradual growth in support over the short term, hoping for a third-place finish in Iowa, followed by second in New Hampshire and first in South Carolina -- proceeding from there to roll up victories and strong finishes as the non-outsider pick.
Third in Iowa seems like it's the likeliest outcome. From there? We shall see.
Philip Bump writes about politics for The Fix. He is based in New York City