Washington ? Mitt Romney hit an off note when he told a “humorous” story about his dad shutting down a factory.

Robert De Niro managed to get both Newt Gingrich and the Obama campaign riled up when he joked at an Obama fundraiser that America isn’t ready for a white first lady.

Texas Gov. Rick Perry, still nursing wounds from his failed presidential campaign, did himself a world of good with his self-deprecating jokes at a recent Washington dinner.

Done right, humor can be a huge asset for a politician. But it is fumbled easily in the overheated environment of a political campaign.

That may be why Romney’s aides sent him to the “The Tonight Show” this past week with these instructions: “Don’t try to be funny.”

The Republican presidential front-runner largely complied, and that worked out just fine for him. But he apparently forgot his advisers’ advice the next day when he attempted to be funny on a conference call with people in next-to-vote Wisconsin.

Romney recounted what he called a “humorous” story about the time his auto executive father shut down a factory in Michigan and moved it to Wisconsin. Later, when his dad was in a parade while running for Michigan governor, the marching band kept playing the University of Wisconsin fight song.

“Every time they would start playing ‘On, Wisconsin! On Wisconsin!’ my dad’s political people would jump up and down and try to get them to stop,” Romney said with a laugh.

Democrats pounced on it as fresh evidence that Romney is out of touch with the economic concerns of ordinary voters.

Jokes that might be funny another time often don’t pass muster under the klieg lights of a presidential campaign.

President Barack Obama, for his part, has had better luck using humor to deflect questions about his own vulnerabilities.

During a St. Patrick’s Day reception this month, Obama was presented with a certificate of Irish heritage by the Irish prime minister.

“This will have a special place of honor alongside my birth certificate,” Obama deadpanned, deftly sending the message that any lingering doubts about where he was born are nothing but a joke.

Sometimes, humor can come back to bite a candidate long after the laugh lines have faded.

In 2004, when Romney was Massachusetts governor, he took a jab at the wealth of that year’s monied presidential candidate, Democratic Sen. John Kerry.

“There’s a senator from my state, you may have heard, that wants to get elected president,” Romney said at a dinner. “And I don’t know why he wants to do that because, of course, if he won he’d have to move into a smaller house.”

It may have been funny then, but the joke boomeranged when it resurfaced on the Internet this week just as Romney is trying to combat an elitist image.