What is it about Antonio Villaraigosa that leaves him stumbling just as he nears the finish line?

Up until last week, Hahn campaign advisors were so gloomy about the runoff election that they were suggesting privately that the incumbent mayor’s only hope was a low voter turnout. Conservatives, who tend to vote in higher proportions than the general electorate, are a major target for the mayor.

“The trick is for Hahn to keep the more liberal voters, the ones more likely to support Antonio, at home,” said one adviser.

But then came the revelation that Villaraigosa had received $31,000 in campaign contributions from individuals in Florida with ties to an airport concession company. And before that came lackluster debate performances that had the city councilman answering questions vaguely or avoiding them altogether.

As of late last week, it was unclear whether any of this would seriously eat into what’s been a double-digit lead over the mayor. But it’s bound to raise questions about Villaraigosa’s ability to “seal the deal.”

It’s especially striking given his collapse four years ago when Hahn’s campaign aired a commercial saying that Villaraigosa had sought a presidential pardon for convicted cocaine dealer Carlos Vignali. Villaraigosa’s initial response did not address the central premise of the ad, which was true. Within days, his poll numbers plummeted and he lost support among conservative white voters.

Predictably, the Hahn campaign quickly seized on the recent news reports about how at least 20 employees of Miami-based Travel Traders Inc. and related entity S.E. Florida Investments made contributions to the Villaraigosa campaign. The president of Travel Traders, Sean Anderson, had previously headed the U.S. travel retail business for W.H. Smith Group, which had a major concession contract at Los Angeles International Airport.

When the Torrance-based Daily Breeze, which broke the original story, and the Los Angeles Times called the employees, some responded that they had no idea who they contributed to when they wrote their checks.

Under city campaign laws, it is illegal for any of these employees to be reimbursed by either of the corporate entities. So far, no evidence of reimbursements has surfaced, but the Hahn campaign has asked the city Ethics Commission to investigate.

What was missing in the initial hours after the story broke was any substantive rebuttal from the Villaraigosa campaign and from the candidate himself. All that could be mustered up was a statement that “if there are questions about contributions, we will look into them immediately and take action.”

That was not unlike the initial response to Hahn’s TV ad in 2001, which first aired 10 days before the election. Villaraigosa called the ad “reprehensible” and said Hahn had sunk to a new low, but he never addressed the ad’s central point that he wrote a letter seeking a pardon for Vignali. It wasn’t until days later that he publicly acknowledged writing the letter, and he never counterattacked against Hahn.

This time, beyond the mysterious contributions from Florida is a 90-minute dinner meeting last fall scheduled to include Anderson, Villaraigosa and L.A. lobbyist Art Gastelum, who has represented W.H. Smith. Gastelum was called to testify before an L.A. County grand jury that was probing “pay-to-play” allegations in the awarding of airport contracts, according to news reports.

“What was Antonio thinking when he met with Art Gastelum along with this Anderson fellow?” said one political source not affiliated with either campaign. “It shows incredibly poor judgment.”

More broadly, the Florida contributions follow a period in which Villaraigosa was seen by some in the local political community as coasting on his substantial lead and not showing the same passion and energy that a scrappy challenger should. In fact, the Los Angeles Times remarked in an editorial after a recent debate that Villaraigosa “had checked his charm in at the door.”

“Villaraigosa has to show he can manage this crisis effectively,” said political consultant Richard Lichtenstein, who is not affiliated with either campaign. “So far, it has not risen to the level of reversing the momentum, though if it becomes what the rest of the campaign is about, that’s another story.”

Meanwhile, turnout is already expected to be well below the levels for the last two mayoral runoff elections in L.A. In 2001, when Hahn defeated Villaraigosa by seven points, turnout was 38 percent. In 1993, when Richard Riordan defeated Michael Woo, it was 43 percent.

This time, unofficial estimates have turnout in the low 30-percent range, with some suggesting it could even dip below 30 percent. “Lower Latino turnout hurts Villaraigosa and helps Hahn,” said Raphael Sonenshein, professor of political science at California State University Fullerton.