With election season heating up, it’s hip to wear your politics on your sleeve.

Politically charged T-shirts and tank tops have become a favorite fashion statement this summer. Not surprisingly, celebrities are at the forefront of the trend.

Actor Jack Black (“School of Rock”) was recently spotted sporting a “Vote for Kerry” tee, Spanish actor Javier Bardem (“Before Night Falls”) wore a “Stop Wars” shirt with a logo modeled after the one for “Star Wars” and “Sex and the City” costume designer Patricia Field is selling “Let’s Vote!” tops in her SoHo boutique.

But it isn’t just a fashion fad that’s fueling the T-shirt trend. It’s pure, unadulterated passion about politics.

“There’s a lot of emotion running around this election,” said fashion expert Elycia Rubin, author of the forthcoming book “Frumpy to Foxy in 15 Minutes Flat.” “Celebrities and people in general are really showing that emotion by wearing these shirts.”

Interest in the political race is also unusually strong, according to Fox News political analyst Eleanor Clift, who pointed to a recently released Pew Center survey as evidence. The survey found that 64 percent of the population is paying close attention to this presidential election, compared with less than half of voters four years ago.

“There’s a heightened interest in this election,” said Clift, a Newsweek contributing editor. “It’s like you’re rooting for your team and you want to sport the paraphernalia that shows what side you’re on.”

Everyone from the average Joe to the rich and famous is donning a top to express his views and try to influence others in the process.

“It makes people feel in some way that they’re making a difference,” Rubin said. “By wearing this shirt, they’re putting a message out there.”

In addition to Field’s tank tops and T-shirts, which go for $28 at her store and online at www.patriciafield.com; Audrey Roberts sells the “Vote for Kerry” Ts for $20 and several shirts encouraging voting are available on www.declareyourself.com for $20, including a “Gone Voting” T by designer Todd Oldham. A company called The Right Things offers tops with slogans like “No Left Turns” and “George Bush for President 2004.”

Some of the shirts, on both ends of the political spectrum, have a sense of humor. Among the offerings for the right-of-heart: a T-shirt showing a toilet that says, "John Kerry, John Edwards. Flush the Johns Nov. 2nd!", a shirt with the slogan "Fahrenhate 9/11" and a top that has John Kerry's name above a picture of flip-flops with a red line through it declaring, "No flip-flops in the White House."

Those on the left side of the aisle have plenty to choose from too: a shirt that has a photo of Bush with horns on his head and the slogan "Stop Mad Cowboy Disease"; a tee showing a pooch lifting its leg over a shrub that says, "Dogs for Kerry: Bushes Are Only Good for One Thing" and a top facetiously urging people to "Re-Elekt Bush."

While many celebs aren't shy about letting the world know their political leanings, others are more interested in simply encouraging people to get involved in the process.

Field said Paris Hilton and Britney Spears are among the stars who have gotten decked out in her “Let’s Vote!” shirts. Yoko Ono also purchased one, according to Field.

“Many celebrities have come in and bought them,” she said. “And since they’re celebrities, they’re seen. Maybe they’ve decided they want to be a billboard.”

Field helped design the tanks and tees to raise awareness and persuade voters to go to the polls.

“I wanted to raise the consciousness, particularly of young people whom I believe do not take part in the political process,” she said. “It’s very necessary to get them in on the process because it could change the nature of things in our country.”

In addition to getting out her “Get out the vote” message with shirts, Field also distributes voter registration forms in her store.

And from the looks of it, more people will be heeding Field's advice this year. This presidential election centers on issues Americans feel particularly strongly about, like the economy and the war in Iraq.

“Four years ago, they called it the 'Seinfeld' election because it wasn’t about much of anything,” Clift said. “You’ve got some pretty serious issues this time. People are more engaged.”

Recent phenomena like Bill Clinton’s just-released memoirs and Michael Moore’s anti-Bush documentary “Fahrenheit 9/11” have helped drive interest in what’s going on in Washington.

“Politics is crossing over into pop culture,” Clift said.

And the election-minded tees and tanks are just another manifestation of that trend.

“It’s sort of a trophy you want to have to show this is what you’re standing for,” said Clift. “It’s cool to find this election interesting.”