Washington (CNN)One thing jumps out about the field of serious Democratic challengers to President Donald Trump in 2020: almost all of them are US Senators.
A lot of Democratic senators want to be President. History shows it will be hard.
But history shows some of those big names -- such as Bernie Sanders, Cory Booker, Elizabeth Warren, Kirsten Gillibrand and Kamala Harris -- may face an uphill climb from the Senate to the West Wing.
Over the last two and a half centuries of American politics, sitting members of the US Senate have not fared well in presidential elections. Only three Presidents have ever been elected from their seat in the Senate: Warren Harding, John F. Kennedy and Barack Obama.
Three of the last five presidential losers -- John McCain, John Kerry and Bob Dole -- all tried (and failed) to move to the Oval Office from the Senate chamber. And we saw in the 2016 Republican primary that a slew of Senators -- Marco Rubio, Ted Cruz, Lindsey Graham and Rand Paul -- couldn't win their party's nomination.
"The skills traditionally associated with US Senators (and I say traditionally for a reason) do not translate to presidential campaigns well or easily," explained Anita Dunn, a top aide to Obama's campaign in 2008, in an email to CNN. "Senators, by and large, aren't executive types who have managed large organizations. A modern Presidential campaign is a billion-dollar business built in a very short period time."
Overall, 16 presidents served in the Senate at some point in their careers, but most of them served in high-level executive or foreign policy positions before moving to the Oval Office. The most common job prior to the presidency that involves time spend in the upper chamber is the vice presidency, a good sign for former Vice President Joe Biden, who has said he'll make a decision on a future run by the end of the year.
Another common path for Senators to bolster executive and foreign policy experience came from serving as a governor, Cabinet secretary or ambassador, though all the success stories from this group came before the end of the Civil War.
As for those elected commander in chief who did not spend time on the Senate floor? Seventeen of them served as a governor, including four of the last seven presidents. Some potential 2020 Democrats in this category include Montana Gov. Steve Bullock, Los Angeles Mayor Eric Garcetti and New York Gov. Andrew Cuomo.
This executive experience is important to voters. A Suffolk/USA Today Poll in 2015 found 40% of Americans preferred a candidate with experience as governor compared to only 23% who chose a candidate with Senate experience.
Furthermore, the percentage of Americans who prioritize legislative over gubernatorial experience has been steadily decreasing over the last three decades, according to the Pew Research Center. In 1987, 66% of Americans thought that a member of Congress was better prepared to be President versus 22% who chose a governor of a state. In a 2014 survey, those two numbers were dead even at 44%.
The news isn't all bad for senators who have their eyes on the White House. Of the three to make the leap, two of them came within the last half century, including Obama in 2008.
"Obama had the advantage of not having been in the Senate very long - fewer problematic votes, and he hadn't gotten the Senator mind-set yet," said Dunn. "Senators who run for President, unless they have decided they are up or out, tend to keep one foot back in the Senate for far too long - they worry about missing votes, voting percentage, they actually have to get back to cast votes, and they have entire states of constituents and state interests that have to be factored into their national platforms."
Another promising sign for these Democratic hopefuls? Recent polling indicates that Democrats are more open to the idea of electing a senator to the White House. A Quinnipiac poll in 2015 found that a majority of Democratic voters, 58%, preferred a member of Congress to serve as President, compared to only 38% of Republicans who thought the same.