Democratic presidential candidate Hillary Rodham Clinton speaks at an event...

Democratic presidential candidate Hillary Rodham Clinton speaks at an event at Rancho High School, Tuesday, May 5, 2015, in Las Vegas, Nevada. Credit: AP

Martin O'Malley has good abs. And wasn't he was once mayor of Baltimore?

That seems to be about the sum of what most Americans know about the former Maryland governor as he prepares to launch a presidential bid on May 30. O'Malley polls somewhere between zero and 2 percent in early Democratic primary surveys, a dozen points behind Massachusetts Sen. Elizabeth Warren, who's not even running.

O'Malley's bleak numbers remind me of a former New York State senator who put his hat in the ring for mayor of New York in 1977. His pollster had good news and bad news, he once told me. The good news was that he was at 3 percent in the latest survey. The bad news was that the poll had a 4-percent margin of error. He could be at negative one.

But O'Malley is suddenly interesting, far more so than his anemic poll numbers would typically warrant. He matters because he's the sole candidate in the current Democratic field who could legitimately step in as the party's standard-bearer should Hillary Clinton's candidacy collapse. Vermont Sen. Bernie Sanders (12 percent in the latest Economist survey) is an avowed socialist, which, thankfully, still makes him a non-starter in American politics. Vice President Joe Biden (11 percent), who is reportedly hanging around in the wings in case Clinton tanks, remains America's favorite crazy uncle. He's a hoot at Thanksgiving, but you don't want to see him behind the wheel.

O'Malley comes out of central casting. He's handsome, articulate and passionate about his beliefs. He stands decidedly to Clinton's political left, but he has the clean-cut looks of someone who wouldn't spook the American public in a general election. Indeed, when he's not posing shirtless for cameras in beach photo-ops, he looks like the Brooks Brothers conservative Aaron Sorkin might conjure for a new HBO series. And at 52, O'Malley is vibrant. He appears to be reaching his prime, whereas Clinton, rightly or wrongly, seems to have exceeded hers. It's not so much that her past is wearing on her, it's that it's catching up with her.

It's a marvel to watch Clinton at present. It's as if she's suspended in air. She's the prohibitive favorite to be the Democratic nominee while carrying at least 1,000 pounds of baggage, with more seemingly being added by the day. The big question is whether she can continue to defy gravity. It's possible she can. But it's probable that she eventually falls to earth.

O'Malley's positioning as the dark horse candidate in the race isn't escaping notice. Political blogger Matt Drudge had a field day this week reciting past praise heaped on O'Malley by none other than former President Bill Clinton. Mr. Clinton sang O'Malley's praises liberally at the 2014 annual meeting of the Clinton Global Initiative. In a 2002 letter to then-Baltimore Mayor O'Malley, the former president wrote, "I won't be surprised if you go all the way." Say what you will about Bill Clinton, he has a good eye for political talent.

I recently asked a prominent New York Democrat in a television green room -- a progressive Democrat -- what's wrong with O'Malley? Why aren't more left-wing Democrats backing him? He was genuinely perplexed by the question. There's nothing wrong with O'Malley, he said, but why on earth would we mess with a good thing? In other words, Clinton is the surest thing they've got going into 2016.

She certainly is. So long as she can remain suspended above ground. But if she's ever forced to touch terra firma, watch for O'Malley to be there to meet her.

William F. B. O'Reilly is a Republican consultant.

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