The top Democrats who could challenge Trump in 2020

President Donald Trump has been in the White House less than 100 days, but frustrated Democrats are already looking ahead to the 2020 elections.

That tantalizing prospect of getting a Democrat back in the White House after four years is expected to attract an unusually sprawling field of candidates that could include everyone from senators and governors to actors and businessmen.

And unlike the previous two Democratic nominating races, the contest will begin with no clear frontrunner and a leaderless party, leveling the playing field and inflaming the imagination of any public figure spoiling for a possible fight against one of the most polarizing presidents in memory.

The Iowa caucuses are over 1,000 days away and the political landscape will undoubtedly change in unpredictable ways in the meantime. But the prospect of taking on a controversial and unpopular incumbent who lost the popular vote in 2016 has potential candidates are already starting to think about it. Here are some people to watch:

Remainders

Other governors - Connecticut Gov. Dan Malloy was called Obama's favorite governor, and he's now leading the Democratic Governors Association, raising his profile and connecting him to donors, elected officials and operatives across the country. Colorado Gov. John Hickenlooper, a former brewpub owner, has been eyed as a different kind of Democrat from a swing state. Washington Gov. Jay Inslee's administration has scored victories against the Trump administration in court. And even Virginia Gov. Terry McAuliffe, the longtime party fixer and fundraiser, has left the door open on 2020.

Other senators - Sen. Chris Murphy (D-CT) has carved out a prominent spot in the party as a young foreign policy expert. Franken's home state colleague, Sen. Amy Klobuchar, is said to be interested in a White House bid. Sen. Tammy Duckworth (D-IL) is a Purple Heart-winning vet who ran a successful race to be promoted from the House. And Sen. Sherrod Brown (D-OH) inspires fandom in may progressives while remaining popular in the kind of blue-collar areas where Trump routed Democrats.

Wildcards

Then there are the businessmen and women, the celebrities, the non-politicians. Trump won, their thinking might go, so why not me? Facebook executive Sheryl Sandberg has been rumored to be interested, as has Starbucks CEO Howard Schultz. Mark Cuban, the billionaire "Shark Tank" star, brings a unique ability to get under Trump's skin. And rumors even fly about actors like Dwayne "the Rock" Johnson and George Clooney.

Unlikely? For sure — but so was Trump.