But no matter how much distance individual Senate candidates put between themselves and the 2020 primary, running away from the party’s presidential nominee rarely works and might not be much of an option. That’s why different Democratic factions are already arguing that their candidate is more likely to notch the seats needed to make Chuck Schumer majority leader.

“It’s the presidential race that's going to drive turnout and energy, even as important as these Senate races are,” said John Walsh, who dropped out of the Colorado Senate primary to endorse Hickenlooper. “Democrats need someone they can be united around.”

For moderates, Biden is the obvious choice, and he made this case himself in the most recent Democratic primary debate. As someone who was on the ticket with Barack Obama and won states like North Carolina and Indiana in 2008, Biden’s claiming he’s the guy that can put in play Senate races in North Carolina, Georgia and Iowa.

Poll averages show Biden more competitive in North Carolina, a state where Tillis is seen as vulnerable and that Democrats almost certainly need to win to cobble together a Senate majority. To gain power, Democrats need three seats and the presidency or four seats without it.

Nationally, the idea that Biden can expand the map has become the conventional wisdom for both parties.

“Certainly, a Biden, a more moderate candidate, makes the path a little bit easier,” said Sen. Doug Jones (D-Ala.), the most vulnerable Democratic incumbent and a Biden supporter. “And others would make it more narrow.”

Republicans are eager to portray Democrats as wild-eyed socialists, an argument most privately admit doesn’t really work against Biden’s incremental progressivism. Far better, they say, for Democrats to nominate someone firmly on the left whose policies create constant tension with more centrist congressional candidates.

“If Democrats nominate Elizabeth Warren or Bernie Sanders, people are going to say: ‘I may not be the president’s biggest fan, but I don’t want any of that,’” said a Republican senator up for reelection next year.

That’s what the center-left argues, too.

“Moderate Senate candidates would prefer to run with a presidential nominee at the top of the ticket who supports the same health care, tax and environmental policy that they do,” said Jon Kott, a former Joe Manchin aide who runs a new group called Majority Makers to help centrist Democrats. Otherwise, they’ll need “to demonstrate their independence from the national political party.”