Hosting an event during the political conventions is no minor investment for the corporations, lobbyists and interest groups behind these shindigs.

It takes months of planning and typically more than one trip to the convention cities. The price tag just to co-sponsor a high-profile bash can run into six figures, while smaller affairs can set back the budget $50,000.

And then there’s the constant worry: With more than 600 sideshows planned over the next two weeks in Denver and the Twin Cities, how does a corporation or group get any bang for those considerable bucks?

“It’s really a challenge, especially this year when you look at the Democrats’ list alone, 15 pages of events. My head spins,” said Adrienne Levey Johnson, who runs Spellbound Creative Concepts and is planning several convention events including two for automaker Daimler AG in Denver and Minneapolis. “There’s tons of competition.”

But party planners, lobbyists and corporate and association leaders say the money and time spent hosting an event at the conventions can pay off, even if in the subtlest of ways. For one, it gives executives and lobbying clients a chance to mingle with a cast of political VIPs that assemble only once every four years, providing a rare opportunity for face-to-face schmooze time.

Convention functions also help companies and groups step up their image with this highly targeted audience, and some infuse their functions with a big dose of policy.

It’s also what everybody else is doing, so it’s the place to be seen as a player, especially with clients.

“During the convention, any lobbyist becomes a glorified concierge,” explained K Streeter Heather Podesta, who runs Heather Podesta + Partners. “And it’s important to be able to take care of clients and to entertain clients.”

Along with her husband, Tony Podesta, founder of the Podesta Group, Heather Podesta is hosting two brunches and a book party this week in Denver.

Party invites, she said, are the “currency at the conventions,” and when you have invites to pass out, you see returns in the form of invites to other exclusive soirees.

Location is also key when it comes to putting on a party. The hottest venues in Denver are restaurants, hotels and other spots in the downtown area near the Pepsi Center.

In the Twin Cities, by contrast, most of the corporate events are scheduled for Minneapolis, while the convention itself will be in St. Paul’s Xcel Energy Center.

Podesta said that in addition to location, the trick to hosting a successful event is providing good food and drink.

That’s one thing that Democrats and Republicans can agree on.

“For me, what makes a successful event: good music, good food and good booze,” said Rob Jennings, whose company, American Events Consulting, is putting on several productions in Denver and the Twin Cities, including a southern delegation party in Minneapolis featuring rocker Sammy Hagar. “We’re looking for a broad appeal, something for the 21-year-old and the 70-year-old,” he said.

Monica Notzon, founder of the GOP fundraising firm Bellwether Group, said many of her clients are feting convention-goers in the hopes of gaining some name recognition.

“From our perspective, a number of our clients may be lesser-known associations, so for them it’s really about brand identity,” Notzon said. “It’s about branding their association and helping people to understand what their association is and what kind of projects they’re working on.”

One such client is the Bipartisan Policy Center, a group founded last year that includes former Sens. Bob Dole (R-Kan.), George Mitchell (D-Maine) and Tom Daschle (D-S.D.). To hype up its bipartisanship, the group took on the theme “Two Parties, One Ticket” — one ticket to get into events in Denver and Minneapolis/St. Paul.

Jeremy Bayer, the Bipartisan Policy Center’s director of corporate partnerships, called the parties a good investment for the group, though he declined to put a price tag on the two events.

We think in order to frame the BPC in the way it needs to be framed, getting the name out there and letting people know it exists, we just thought it would be a good opportunity at both conventions,” he said. “We’re definitely doing it to get our name out there. And there isn’t a better place, if you want to get your name out. It’s a very targeted audience.”

But for other companies, branding is not the issue, at least not entirely.

Johnson & Johnson will host parties at the conventions, including one in Minneapolis honoring the moderate Republican Main Street Partnership. The idea, said J&J spokesman Marc Monseau, is to allow delegates and attendees to meet and talk on a wide range of topics, including health care.

“It’s not really about name branding. It’s about creating a space for the delegates to meet and talk, and the events that we end up sponsoring reflect the diversity of our companies,” he said.

Not everyone is in the party spirit, though.

Veteran BKSH lobbyist Chuck Merin said the new ethics restrictions have stripped the convention of some of its best lobbying opportunities; he’s giving Denver a pass, the first convention in more than 20 years that he’s not attended.

“Given the heightened sensitivity to lobbyists and lobbying and new disclosure regulations, they preclude a lot of the more targeted opportunities, small lunches and dinners,” Merin said. “Participation at the conventions is not as rewarding as it has been in the past.”

But based on the number of corporate sponsors and convention events, that’s apparently the minority view.