While many celebrities followed politicians at last year’s conventions, they were being followed by an Oscar-winning filmmaker.

“Rain Man” and “Good Morning, Vietnam” director Barry Levinson foresaw the pre-election Democratic and Republican gatherings as target-rich environments for making a documentary about the modern connection between Hollywood and politics. Titled “Poliwood,” the 90-minute result has its Showtime debut today.

“I assumed it was not going to be easy,” Levinson says of working amid such hectic events, “but we sort of naively went along and saw what we could do. We ended up having enormous access as we followed a group through the two conventions, then up to inauguration weekend. What this evolved into is what I look at as the intersection of politics, celebrity and media.”

In preparing “Poliwood,” Levinson consulted the Creative Coalition, an entertainment-industry organization whose partial purpose is nonpartisan political advocacy. One of its two current presidents, Tim Daly, is a producer of “Poliwood”; he also appears in the documentary, as does his co-president, Dana Delany.

So do Susan Sarandon, Anne Hathaway, Sting, Fergie, Annette Bening, Danny Glover, Hayden Panettiere, Alfre Woodard, Ellen Burstyn, Spike Lee, Zooey Deschanel, Elvis Costello, David Crosby and Maura Tierney, among others.

“It’s a bit of a circus,” Levinson says of filming at a convention. “In some ways, you just kind of go with the flow. We wandered in and out of a number of things, met people along the way, and just kept filming.”

Levinson says his incentive for making “Poliwood” was his sense that “we have a really serious problem that I don’t know we can ever recover from. News was originally a public service, then they realized you could make money with it. Then you’ve changed the concept of news and what it represents, and you have to continue to up the stakes, so you borrow tricks from entertainment.

“Then you’re beginning to go down a different road, and you end up with the concept of the left and the right, and confrontation and polarization.”