Perhaps it’s the lure of the road. Or the long-repressed teenage desire for the life of a rock star or the life of a presidential candidate.

Or maybe it’s all just an elaborate excuse to get out of D.C.

Whatever the reason, K Street has an infatuation with August recess road trips. These odysseys always have an official mission: to register like-minded voters, to galvanize the grass roots on a legislative issue or to make pit stops with Congressional candidates in places like DeKalb, Ill., and DeKalb County, Ga. And Portland, Ore.

In 2006, the U.S. Chamber of Commerce debuted its Business Bandwagon, a 45-foot-long bus bedecked with leather seats, wireless Internet and ceiling mirrors festooned with tiny white light bulbs.

“I keep expecting Britney Spears to walk out of the bathroom any minute,” a chamber employee told me during the vessel’s maiden voyage to Annapolis, Md.

The bandwagon hit the pavement again in 2008, making stops at the presidential nominating conventions, but it’s unclear whether it will reprise this year. “We haven’t committed to a bus tour,” a chamber spokesman said in a recent e-mail exchange.

But even if the big-business lobby decides to put the brakes on its trip, the Service Employees International Union is gassing up a bus in California and won’t let the August tradition fall by the roadside.

The union’s executive vice president, Eliseo Medina, is organizing a San Diego-to-Sacramento tour to encourage Latinos to register to vote and to fight anti-immigration measures. It will begin Aug. 14 and last four days.

“We see the climate in Washington — it’s so poisoned,” Medina said in a telephone interview last week from Southern California. “Not only is immigration reform probably not possible … but we want to be able to say to the community, whether you are a Republican, Independent or Democrat, you’ve got to vote.”

But why a bus tour when there are other, sometimes cheaper, ways to get the message out? Indeed, the Pharmaceutical Research and Manufacturers of America has suspended its Partnership for Prescription Assistance bus and opted instead for high-tech BlackBerry and iPhone applications to spread the word.

“It basically goes back to our roots,” Medina said. “I started out working with the Farm Workers unions, and we had a bus tour — 50 of us got on an old school bus in the middle of winter and wound up in New York City.”

That was in 1968, but the craving for retail politics, or retail advocacy, hasn’t faded.

The chamber’s J.P. Fielder recalled one of his better moments from the long, hot Vote for Business Bandwagon tour in 2008. He and his colleagues stopped in the Lower 9th Ward of New Orleans for what was supposed to be a brief service project with Habitat for Humanity.

“Instead we stayed most of the afternoon and drove in the night to get to a Pete Olson endorsement event in Houston,” Fielder recalled, referring to a Republican Congressional challenger who was elected that fall. “It was blazing hot and the area was just devastated. But everyone who had moved back in came out to check out the chamber’s giant ‘Vote for Business’ bus.”

Medina puts it this way: “When you get on the road, it provides a point of focus. It’s not an isolated event, but indicative of a movement that is coming together, people working together for the common good.”

It’s different, Medina added, than just flying into a city for a meeting and then flying back out. A bus trip “really implies much more sacrifice,” he said.

In the SEIU’s upcoming California bus tour, Medina and his allies will be up early in the morning and driving late into the night, then crashing at Motel 6 in different cities.

“It’s going to be so exciting,” he said, completely serious. “It’s empowering. There’s positive energy that gets released and people like to feel like they have some control.”

But don’t expect the SEIU’s to be a fancy ride. “It’s not quite the same as if Madonna showed up,” Medina joked. “For us to show up in a rock-star bus would be a way to ensure that people would tune us out.”

Patrick Ross, executive director with the Copyright Alliance, won’t even have a bus at all for his recess road trip. He’s renting a hybrid vehicle for his voyage to meet with artists in 35 states to highlight to Members the importance of strong copyright laws on their individual constituents.

Ross will start in New England, head for the mid-Atlantic, then go to the South, work his way through the Midwest and Mountain West and end up in the Pacific Northwest. He won’t divulge the names of the artists he’s meeting with, but he said he’ll have a sit-down with a graphic novelist in a Southern town of 1,245 people and another one with a Delta blues musician in New England.

“Part of the reason I’m going out to them, it’s not just because I love driving six to eight hours a day and staying in Best Westerns, although I’ll be doing that, but they’re often leaders in their communities, their art reflects their environment,” Ross said recently. “These are not lobbyists, not policy activists.”

For a few legs of the trip, Ross is bringing along his 15-year-old daughter to serve as his videographer, but most of the time it will be just him.

“I’ve never done anything quite like this before,” Ross said. But he started interviewing artists when he found himself in their towns on business and decided he needed to do more to bring visibility to the alliance’s Creators Across America campaign.

“I drove out here from LA 21 years ago, and I’ve always wanted to drive cross-country again,” he said. “I was in a rush then, and now I’m in a rush because I need to get all these interviews in. So it’s still not quite the romantic road trip that I had anticipated, but I’ve got to do this before I’m too old.”