If Joe Biden was trying to unsettle Hillary Clinton by meeting with Elizabeth Warren over the weekend, here's a way to really rattle her: pick the Massachusetts senator as his presidential running mate and announce it now.
Vice President Biden may or may not be serious about challenging Clinton, but one thing is certain: He can't beat her unless something dramatic and unexpected happens.
That's what a Warren selection would be.
There is precedent. In 1976, Ronald Reagan, the champion of Republican conservatives, picked Richard Schweiker, the liberal Pennsylvania senator, to be his running mate about a month before the party's convention. It almost worked.
The concept makes sense despite the tradition of waiting until the convention. It's more transparent for voters as well as party leaders, and it might forestall a panicky last-minute selection of a problematic pick like Sarah Palin.
Leave aside for now whether it's a good governing move. The politics would give a boost to the vice president's steep uphill climb if he decides to run.
Under normal circumstances, Biden would have a tough time raising campaign funds against the vast Clinton money machine. Warren's serious fundraising apparatus would help, though it wouldn't level the playing field.
Warren would also help Biden parry complaints by Democratic women who'd consider his candidacy a threat to undermine the best chance ever to elect a female President. And it would give him a way to soothe Democratic leftists who'd otherwise be irked by his challenge to their candidate, the Vermont socialist Bernie Sanders. Warren is the only elected official who rivals, or exceeds, Sanders's popularity in those circles.
A Biden-Warren ticket would churn stomachs in the Clinton ranks, where there's already plenty of heartburn over the candidate's handling of her private email accounts while she was secretary of state.
Clinton still would be a solid favorite to win the nomination and a Biden-Warren ticket would have challenges of its own. Biden, who twice before has run for his party's nomination, can be a loose cannon, and Warren is untested in national politics.
She has accused President Barack Obama's administration of coddling Wall Street and would have to figure out how to credibly absolve the vice president of the charge, which she also has leveled at Clinton.
When Reagan picked Schweiker in 1976, it temporarily halted President Gerald Ford's momentum toward securing the nomination. Ford prevailed, but only after narrowly defeating a Republican Party rule proposal that would have required him to announce his running mate too.
If Reagan instead had won the rules skirmish, forcing Ford to name his controversial choice, Kansas Sen. Bob Dole, before wrapping up the majority of delegates, more than a few experts thought it would have swung the nomination to the California conservative.
In 1988, after Dole won the Iowa caucuses, some of his advisers urged him to announce the selection of former Tennessee Gov. Lamar Alexander to be his running mate. They reasoned that doing so would give Dole a way to dominate the political dialogue leading up to the New Hampshire primary, blunting expected attacks from Vice President George H.W. Bush. Dole declined. Bush mounted a successful offensive, then won the New Hampshire primary, the Republican nomination and eventually the Presidency.
Albert R. Hunt is a Bloomberg View columnist.