You just can’t trust U.S. Sen. and gubernatorial candidate David Vitter, according to a new attack ad playing widely on television.

“We all know David Vitter breaks his word,” says a female narrator hired by Louisiana Rising, a big-money Super PAC supporting one of Vitter’s opponents, Public Service Commissioner Scott Angelle. Contrast that with Angelle, who, she says, is “faithful to his word” and “a man you can trust.”

Any guesses as to what she’s talking about?

If you said education policy, well, you get a gold star.

The ad’s nominal topic is the highly contested Common Core standards, specifically Vitter’s uncharacteristically clumsy conversion from proud advocate to fierce critic. The commercial shows Vitter on split screen, in his own ad calling Common Core “part of Washington’s dangerous plan” and in a 2014 C-SPAN interview saying “I strongly support the Common Core standards.”

And if the ad’s carefully chosen language made you think of something else entirely, well, you get a gold star, too, for comprehending the larger context.

Vitter’s faithfulness and trustworthiness are very much on the table during the campaign for governor, not because he switched positions on one issue but because of the elephant that’s accompanied him to every room he’s entered since 2007, when he admitted to a “very serious sin” after his name was discovered in the records of a Washington, D.C., prostitution ring.

And just as with Common Core, Vitter’s exposure to such attacks is his own fault. He’s just going to have to deal with indirect references like this, as well as more direct questions and comments.

We’ve heard several of those recently, too. At an Alliance for Good Government forum last week, the moderator asked both Vitter and another opponent, Lt. Gov. Jay Dardenne, whether either had ever violated Title 14 of the Louisiana statutes, which refers to the state’s entire criminal code. Dardenne answered with a definitive “no,” but Vitter, a lawyer and veteran of the Louisiana Legislature, claimed to not know quite what Title 14 says.

He went on to call the query a “gotcha” question that’s “not a good public debate question for a discussion about the future of Louisiana.” He also pleaded for his family’s privacy and called the whole issue a plant for Dardenne, who has brought up Vitter’s past directly and who went to snag the group’s endorsement.

There’s no evidence that Dardenne put anyone up to anything, of course, but he doesn’t need to. It’s out there and will continue to be throughout the campaign. The big question is whether voters think it matters as they choose the next governor.

Some Vitter critics have long contended that he needs to explain himself, which is kind of a silly argument.

What about the situation do they think people don’t understand?

The real upside in bringing up Vitter’s past is to knock him off his game, to make him appear as defensive as he did at the Alliance forum, to zero in on the hypocrisy of his holier-than-thou demeanor and, perhaps, even to trigger his well-known temper.

There’s a downside for his opponents, though, and it’s that they risk a backlash if nothing new comes out.

And there’s a big downside for the electorate as a whole.

Even without the scandal, Vitter surely would have employed the tried-and-true frontrunner strategy of avoiding debates and other uncontrolled situations where his performance is more likely to hurt than help his chances.

With this issue always lurking, the last thing Vitter wants is to have to answer for it on television — hence, his decision to greatly minimize televised debates, despite his skill as a debater. That’s frustrating to his rivals, but should be more frustrating for voters hoping to hear the candidates answer substantive questions.

Still, bringing up the scandal holds at least some more promise than it did during Vitter’s far more partisan 2010 U.S. Senate reelection.

This time, voters who are uneasy about the senator’s past have two other Republicans to choose from, namely Angelle and Dardenne, along with Democrat John Bel Edwards. All three, by the way, seem to have perfectly good marriages.

So, yes, talking about Vitter’s troubles is fair game, and we should expect to hear much more between now and Oct. 24.

Whether it’s a winning strategy is a whole other matter.

Stephanie Grace can be contacted at sgrace@theadvocate.com. Read her blog at http://blogs.the advocate.com/gracenotes.

Follow her on Twitter @stephgracenola.