When he jumped into the 2016 presidential race last year, Marco Rubio announced that he would not seek reelection to his Florida Senate seat even if he failed to win the Republican nomination. At the time, this made sense. Unlike Rand Paul this year or Joe Biden in 2008, Rubio represents a large, politically competitive state where he would face serious opposition for reelection. He would be spending a lot of time out of state (and away from the floor of the Senate) on the presidential campaign trail, and keeping a foot in the Senate race might suggest to Republican voters and donors that he was not fully committed to seeking the presidency. Leaving Congress also allowed him to appeal to anti-Washington sentiment in the Republican electorate by rhetorically trashing the place on his way out the door. Even if Rubio lost the Republican nomination, he would have been a logical candidate for vice president on a ticket headed by someone like Scott Walker or Chris Christie.
But now Rubio's unfulfilled presidential ambitions have dictated a change of mind. After swearing up and down ever since he ended his presidential campaign more than three months ago that he would not jump back into the Florida Senate race, Rubio confirmed today that he will indeed seek reelection. He is not being very coy about the reasoning behind this reversal; as the New York Times reported, Rubio wants to run for president again and believes that he would be a weaker candidate running from the private sector.
At first glance, this seems like an odd calculation. Plenty of ex-officeholders, from Richard Nixon to Ronald Reagan to Mitt Romney to Hillary Clinton, have successfully won a major-party presidential nomination. Running for president while out of office frees a candidate from the duties of another position (or from being accused of shirking those duties) and allows him or her to avoid the pitfalls of being forced to take positions on controversial legislation that might later prove politically disadvantageous—as Rubio himself knows well from his Gang of Eight experience. Moreover, Rubio is no shoo-in for reelection this year, especially on a Trump-headed Republican ballot; a defeat would likely be permanently fatal to his presidential chances.
But Rubio's calculus makes a bit more sense if we game out the next four years a bit. First, Trump's nomination makes Hillary Clinton a strong favorite to assume the presidency next January. If she wins, Republicans will spent the next four years in opposition mode, competing among themselves to lead the charge against her administration. And right there in the center of the arena will be Rubio rival—and runner-up in the 2016 Republican presidential race—Ted Cruz. With a Clinton victory ensuring that no incumbent will be running for the 2020 Republican nomination, the stage would be set for Cruz to mount a second presidential campaign of his own. If Rubio no longer served in the Senate, Cruz would be able to contrast his own ongoing legislative activity fighting for the conservative cause (and against Clinton) with Rubio's absenteeism.
Rubio still has a substantial fan base among Republican consultants and high-dollar donors, but his disappointing 2016 candidacy is a much weaker foundation on which to build a second presidential campaign than previous candidates, like Clinton, Romney, McCain, or Reagan, who needed more than one try to win their party's nomination. He may well be worried that leaving the Senate this year would permanently marginalize him as the GOP moves on to other candidates, while remaining in Congress would allow him to rebuild his public reputation. Under the circumstances, Rubio's decision to risk defeat for a shot at another Senate term makes political sense—but it is safe to say that his sights remain set not on the U.S. Capitol, but on a different white building farther down Pennsylvania Avenue.