Some of the most successful political T-shirt designers on  Cafe Press and Zazzle share their tips for what sells:

* Be witty. Good T-shirts capture a wandering eye, so they need to make the point quickly. Laura Eddy offers this advice: "In today's world, we go by keywords. Everything is done in a very sound-byte orientation."

* Don't try too hard. Like all creative fields, T-shirt designers can run into mental blocks. Eddy said she works best when she allows her mind to wander freely.

* Go with your gut. Art is subjective, so what's funny to one person may not be funny to another. With Cafe Press and Zazzle, which print the shirts after they are ordered, it's okay if only a few people like the idea.

* Be timely. The faster you move, the more likely your shirt will sell. Cafe Press has 6 million members, making it a very competitive space.

"Anything we're going to sell that we know we're going to do well on, we have to be quick," Jason Bostic of American Elephant said. He pointed out his Rand Paul shirts, which were uploaded the day after he said, "We've come to take our government back," in his senate Republican primary victory speech.

* Use text. Jim Gamble of Right Wing Stuff has noticed that wordless shirts don't sell as well as those with a clever one-liner.

Bostick agreed and said that words are especially appropriate for shirts that deal with issues, such as those related to immigration or health care.

* Be selective. Even though there's not much cost associated with sticking up any and every design, customers judge your online shop based on what's there.

"I put stuff up there as eye candy. Some people come and they read it and say, 'That's really funny but I'd never wear a shirt like that.' It's the entertainment value that keeps people on the site so long," Gamble said.

Those visits are still valuable, Gamble notes, because he sells web ads on his site that generate thousands of dollars for him monthly.

* Stay in good taste. Racy shirts can be popular, but the designers advise using good judgment when making fun of someone.

Similarly, not every issue warrants comment. Gamble hasn't put anything up about the Gulf Coast oil spill, for example, because, "It's not a funny subject to begin with."

-- Ambreen Ali, Congress.org