Mark Sanford is the gift that keeps giving to Democrats. The latest revelations about his messy personal life has not only further encouraged those hoping the Dems could steal a seemingly safe Republican seat in South Carolina. They’ve caused the National Republican Campaign Committee to bail on the special election to choose a successor to Senator Tim Scott. The NRCC officially waved the white flag on the former governor’s effort to win back his old seat when it announced it would cease sending money to aid Sanford’s campaign.

The only way to interpret that decision is that the NRCC believes the news that Sanford is being taken to court by his ex-wife over an alleged trespassing incident is a crippling blow to his hopes of defeating Democrat Elizabeth Colbert Busch. If he is fated to lose a seat than any competent Republican should hold with ease, then they seem to be saying that he should do it on his own dime rather than with the funds they’ve raised from GOP donors.

This is good news for Democrats, but the lessons of the impending Sanford debacle should also make them think twice about the prospects that they’ll be stuck with Anthony Weiner, the other damaged ex-politician who is trying to wriggle his way back into office. Weiner, who appeared to be re-launching his career by submitting to an all-too-revealing personal profile that ran on the cover of the New York Times Sunday Magazine this past week, got what some are seeing as encouraging news with the results of a new poll about the New York City mayoral race that showed him running second among Democrats.

Sanford is hoping that this latest divorce fallout won’t hurt him once people find out the details. To be fair, if he is telling the truth about the incident it sounds as if what is happening is a case of his ex-wife using an innocent misunderstanding to take revenge on him. But even if that is the case, it’s an untimely reminder of his past bad behavior that is bound to influence wavering voters. He may have convinced a plurality of GOP primary voters in his old district that he should be forgiven, but the odds that a majority of general election voters will agree just got even smaller.

That’s a lesson that should inform Democrats as they contemplate the second coming of Anthony Weiner.

The fact that a new NBC/Marist poll showed Weiner getting 15 percent of the Democratic vote in a New York primary might lead some to conclude that the former congressman could do even better once he starts campaigning and spending the reported $4 million in contributions that have been sitting in his bank account since his 2011 meltdown after his sexting scandal and the lies that led to his resignation. Weiner’s entry into the race shakes things up since without him on the ballot, City Council Speaker Christine Quinn may win the nomination outright. With him, it looks as if she will be forced into a runoff.

But the sanguine interpretations of this poll should be placed in perspective. As Chuck Todd pointed out this morning on his MSNBC show “The Daily Rundown,” Weiner has 100 percent name recognition, something that can’t be said of his potential rivals this far away from a vote. They have room to grow, as they get better known. Weiner does not. If 15 percent is the best he could do now against them, the idea that he is some sort of potential juggernaut is probably a myth. As the New York Times’s Nate Silver also pointed out in his blog, Weiner’s negatives make him a long shot to win the nomination.

But what if Weiner’s financial advantage and the lack of another credible Democratic mayoral candidate from the outer boroughs—as opposed to the Manhattan-based Quinn—does enable him to come out of nowhere and win the nomination the way Sanford snagged the GOP nod for his congressional seat? Though there doesn’t appear to be a formidable Republican in sight to keep up the city’s streak of five straight cycles without electing a Democrat mayor, a backlash against Weiner could turn around the otherwise unpromising prospects of a contender like Joseph Lhota.

There are those that think New York is more sophisticated than South Carolina and that few there will hold Weiner’s bizarre behavior and lies against him. But cynical New Yorkers are also less likely to buy into a plea that Weiner has redeemed himself and should be forgiven the way many in the more religious south might be inclined to do.

As the Times profile showed, Weiner’s personal issues are far from resolved. The idea that the Democratic Party would gamble away their seemingly certain chance of winning back Gracie Mansion on the idea that Weiner deserves another chance would be a colossal mistake. Like the national Republican Party that is pulling the plug on Sanford, Democrats would be well advised to urge their members to pass on Weiner’s comeback.