Biden being Biden, he cheerfully admitted there might not actually be plenty of time. "If I am wrong, I'm dead wrong," he said.

Meanwhile, in Columbus, another congressional star of the 1990s was continuing his on-again, off-again flirtation with running for president. Governor John Kasich has visited some early primary states and touted a balanced-budget amendment, but he hasn't done much to create the infrastructure for a campaign. The Cleveland Plain Dealer rightly describes this strategy as playing hard to get, but for it to work, someone has to be begging you to get in. The Republican mocked reporters—"I’ve been serious about this all along, you’re just catching on," he said—but what he told a crowd outside of Detroit didn't sound like someone ready to launch a full-scale run: "I’d like you to like me, but I’m not going to lay awake at night and if people here say, ‘I just don’t think he’s the guy. I’m cool with that.’"

Biden and Kasich, though, have always been seen as long shots: Biden because of Hillary Clinton's prohibitive presence on the Democratic side, Kasich because of the whole range of obviously eager Republican contenders. But Governor Chris Christie of New Jersey—that guy used to be considered a frontrunner. He's had a rough run of it since, buffeted by the George Washington Bridge scandal and a series of political and economic setbacks in the Garden State. I noted Monday that Marco Rubio's great strength is that although not all Republican primary voters back him, a huge portion of them are willing to do so. Christie faces the opposite problem—more than 50 percent of GOP voters, in an NBC News/Wall Street Journal poll, say they wouldn't consider backing Christie. Meanwhile, his donors are reportedly getting edgy and wondering when he'll take the plunge, if at all.

Now he's insisting to Matt Bai that he's not only able to run and win, he's ready to do so. The vague and late timeline by which Christie says he'll decide (May or June), his polling, and his big campaign idea—a high-risk and oddly timed call for entitlement overhaul—say otherwise.

Against this background, it's no wonder that Ben Carson hastened to say he'll announce whether or not he'll run—but who are we kidding, he will—soon, on May 4 in Detroit, hopefully with Star Wars jokes.

It seems remarkable that the field of candidates might close before the campaign itself has really opened. But the increasing importance of locking down donors and getting a fundraising apparatus in place means that it's harder and harder for a candidate to stay on the fence. With so many candidates in the field, the top campaign talent and best fundraisers may already be locked up, and precious months of cultivating an officially independent super PAC are lost.

The result is that candidates who almost certainly can't win (Carson, who's never run for office and has seemed unsteady on issues) are well-advised to at least enter the race, while candidates who might fare decently (Kasich, a well-liked governor who's run for president before) may be boxed out.