Who Is Still Running for President in 2020

In mid-February 2019, Sanders, 78, announced he would again seek the Democratic nomination for president having lost in 2016 to former Secretary of State Hillary Clinton.

Sanders, a longtime indepedent senator from Vermont who often votes with Democrats, re-enters a world of presidential politics vastly different than his last campaign, in large part thanks to him.

Since launching a underdog effort four years ago which quickly found national support, many of Sanders' policies — such as universal health care and free public college — have become central liberal proposals.

"We began the political revolution in the 2016 campaign and now it's time to move the revolution forward and make sure that vision, those ideas, are implemented into policy," Sanders said in announcing he would run again.

The longtime senator from Delaware-turned-presidential candidate-turned-running mate and vice president announced his campaign on April 25 with a video message.

"We are in the battle for the soul of this nation. I believe history will look back on four years of this president and all he embraces as an aberrant moment in time. But If we give Donald Trump eight years in the White House, he will forever and fundamentally alter the character of this nation, who we are, and I cannot stand by and watch that happen," Biden, 77, said.

Biden, 77, served as former President Barack Obama's right-hand man for two terms and enters a crowded field of Democratic candidates as the immediate frontrunner in name recognition and most polling, even if his age and historically more moderate voting record put him at odds with the party's progressive wing.

Though he skipped the 2016 race after the death of son Beau, Biden hasn't hidden his weighing of a 2020 bid. But his candidacy is not without controversy after he acknowledged that some of his physical behavior, including touching women on the back or kissing their forehead without asking, left them uncomfortable.

In a subsequent video, he said, "I worked my whole life to empower women. So the idea that I can't adjust to the fact that personal space is important, more important than it's ever been, is just not thinkable. I will."

In a highly unusual move, Trump, 73, actually began running for re-election before he was sworn-in for his first term. According to the Washington Post, he was spending money on 2020 efforts as early as Nov. 24, 2016.

The president's surprising win in 2016 has made the pundit class conflicted about predictions for re-election, though the common arguments against Trump include his historically low approval rating, even though presidents are much more often re-elected than not.

As the New York Times detailed in January, Trump may yet face another unusual development: a challenger from within his own party for the Republican nomination. Candidates include former Ohio Gov. John Kasich, a longtime Trump critic, and Maryland Gov. Larry Hogan.

In February, former Massachusetts Gov. Bill Weld, who has campaigned as a Libertarian, confirmed he would challenge Trump as a Republican.

In January, Trump boasted to his liberal opponents: "The Democrats know they can't win based on all of [my] achievements."