Bernstein: Joe Biden is Hillary Clinton's perfect running mate

Joe Biden says he's still making up his mind about whether to run for president. As someone who urged him to pretend to run, I'll say it: Well done, Joe, but it's time to let it go now.

There were good reasons for Biden to pretend to be running for president in 2013 and 2014. The first was a service to the Democratic Party.

To the extent a Biden candidacy could be taken a lot more seriously than, say, a Bernie Sanders run, it was a way for the party and the Barack Obama administration to have a little leverage over Hillary Clinton. Nomination battles normally have the effect of forcing candidates to accept their party's policy preferences. By at least faking a candidacy, Biden was a check on Clinton (just as Elizabeth Warren has been).

He has also helped check Obama. Second-term presidents get into trouble when they think about their place in history and ignore the give-and-take of regular politics. Having a vice president 'campaigning' in 2013 and 2014 encouraged the administration to stay focused on the short- and medium-term effects of the president's actions — a more reliable way of producing good policy than legacy-building exercises.

But in spring 2015, a phony presidential campaign has to do more than have the candidate just happen to schedule events in Iowa and New Hampshire while dropping hints about making up his mind soon. It has to set up field offices and hire staff and raise money. The costs of pretending to run are getting too high.

This doesn't mean Biden has to give up his political ambitions. He's an excellent candidate for another term as vice president, the office he was born to fill. Sure, he's getting a bit old for the job (he's 72 now, five years older than Clinton).

But if Biden ever was in a position to ascend to the Oval Office, under the terms of the 25th Amendment, he could offer to resign immediately after the Senate swears in a new president (who could immediately name him as vice president).

And Joe Biden secures his own legacy as the Practically Perfect Veep.

Jonathan Bernstein is a Bloomberg View columnist covering U.S. politics.