Just how seriously can we take the proposed candidacy of the 73-year-old man who has twice headed poorly run presidential campaigns, and whose greatest notoriety is for sticking his foot in his mouth? A surprise meeting with Elizabeth Warren has heightened speculation in Washington that Biden will make a white-knight run for the nomination, to rescue the party from a Hillary Clinton collapse. But is it too late? The Wall Street Journal’s Carol Lee and Reid Epstein report that the question may be whether time has run out for Hillary:

Vice President Joe Biden, who has long been considering a presidential bid, is increasingly leaning toward entering the race if it is still possible he can knit together a competitive campaign at this late date, people familiar with the matter said.

Mr. Biden still could opt to sit out the 2016 race, and he is weighing multiple political, financial and family considerations before making a final decision. But conversations about the possibility were a prominent feature of an August stay in South Carolina and his home in Delaware last week, these people said. A surprise weekend trip to Washington to meet with Sen. Elizabeth Warren (D., Mass.), a darling of the party’s liberal wing, represented a pivot from potential to likely candidate, one Biden supporter said. …

Mr. Biden would enter as a clear underdog. Polling shows Democratic front-runner Hillary Clinton running far ahead of the vice president, who would be building a campaign team largely from scratch. Mrs. Clinton, who declared her candidacy four months ago, has a robust campaign operation and an outside super PAC raising money on her behalf.

Still, the vice president’s deliberations illustrate how, with just six months before the first presidential nominating contests, both major parties’ campaigns are in a state of flux. Democrats are increasingly insecure about Mrs. Clinton’s candidacy, given her dipping approval ratings and continuing questions about her use of a private email server while secretary of state.

In the Washington Post, Paul Kane and Elise Viebeck mull over the timing from a practical standpoint. It’s not too late yet for another contender to jump into the race, but it’s getting there. That would depend, however, on Hillary leaving the race and releasing her donors and staff. Needless to say, that hasn’t yet happened, which makes a Biden bid almost impossible:

Many observers think he’s already too late. Recent history has not been kind to late-entry candidates (Rick Perry, August 2011; Fred Thompson, early September 2007; Wesley Clark, mid-September 2003). None of them, however, were a sitting vice president with universal name recognition. So, we wait for Biden.

There are several key events, however, that will force action. The first Democratic debate is Oct. 13, and Biden has a standing invite, but only if he’s an announced candidate by then.

The next big target dates: Nov. 9-10. That is when the first deadlines arrive for getting on primary ballots, starting with Arkansas and Texas. And through the rest of November and December come 11 more ballot deadlines, including the all-important vote in New Hampshire (Nov. 27 deadline) and massive states with a huge delegate hauls at stake such as Florida, Illinois, Michigan, North Carolina and Virginia.

So, logistically speaking, early November is the drop-dead, latest point anyone could get into the race and assure ballot access in all critical states.

None of the others had the baggage of two embarrassing presidential runs, either. Perry’s problem wasn’t a late entry anyway; it was trying to run while undergoing post-surgical pain requiring medication. He had plenty of time and room for a campaign, and dominated the race briefly before crashing after a couple of bad debate performances. Fred Thompson had plenty of name recognition, but not much desire to run a traditional campaign. Wes Clark had never run for office before.

None of these examples are on point, especially since none of them involved a race in which one candidate not only dominates the polls but also the donor class and the campaign talent in the field. The only way Biden can compete against that is if he doesn’t have to compete against it at all. Even more than Hillary, the only way Biden can win is to run unopposed.

That’s not to say that Clintonland is taking Biden lightly. James Carville fired a shot across the bow yesterday in a New York radio appearance, reminding John Catsimatidis that Biden has “done it twice, and he hasn’t had the best track record doing it.” When Clintonistas start pulling out the 1987 plagiarism scandal, that’s when we’ll know they’re worried.

Meanwhile, Bloomberg Surveillance wonders about the timing as well as the substance of a Biden run, and offers the inevitable Biden-Trump comparison. Expect to see more of this over the next four weeks or so.