It's probably safe to say that one of Donald Trump's more resonant calls when he ran for president in 2016, was his promise to "drain the swamp."

No matter where you stand ideologically, it's hard not to get frustrated over the seemingly glacial pace at which things get done – or don't get done – in Washington.

HBO's new documentary The Swamp looks at that problem through the prism of three Republican congressmen: Matt Gaetz of Florida (top), a relative newcomer and rising star whose support of Trump has earned him considerable attention; Ken Buck of Colorado, founding member of the conservative House Freedom Caucus; and Thomas Massie of Kentucky (top), a self-described Libertarian Tea Party member.

That might sound like a lineup that would fall right in line behind the president on bashing Democrats, slashing government, ridiculing red tape, and dismantling what they consider reckless liberal giveaway programs, from food stamps to the Affordable Care Act.

There's a bit of that. But that's not the focus of The Swamp, which was directed by Daniel DiMauro and Morgan Pehme.

The two-hour program takes quite a different tack, not only from what we might expect in a highly partisan political age but from how Trump himself seems to have defined "the swamp" since taking office.

For Trump, "draining the swamp" often seems to have meant replacing leaders with whom he disagrees, like former FBI director James Comey or former Federal Reserve Board Chairman Janet Yellen.

The Swamp makes a forceful case that the real swamp has little to do with appointed or elected officials and everything to do with a system in which the primary goal of almost all elected officials has become fund-raising.

The filmmakers and all three of their subjects agree that's dangerous because it forces elected officials to submit to the affection of lobbyists who want Congress to pass legislation that helps their clients, and whose clients can, in return, provide the level of financial support that has become essential for remaining in elected office.

If that sounds like a recipe for corruption, almost a mandate for it, The Swamp makes a strong case that it is.

For instance, Gaetz, Massie, and Buck point out, securing an appointment to a powerful legislative committee comes at, literally, a price. Members of a powerful committee are expected to raise a certain amount of money for the party if they want to remain on that committee – and the party keeps score.

A representative who chairs a powerful committee like Ways and Means, whose purview includes the all-important tax code, keeps the job only if he or she raises $50 million to $80 million a year.

Or, to put it another way, committee chairs are not distributed based on expertise or qualification, but on fund-raising ability – and raking in money on that level is not the kind of thing that can be accomplished by going back home to a town hall meeting and holding a bake sale.

It comes from advocating legislation that would help a powerful industry, like financial or medical or legal, which would, in turn, help steer millions and millions of dollars to PACs and other organizations that would keep their friend in that influential position.

The potential danger in a system powered by special interest money has been recognized and discussed for years. The bipartisan McCain-Feingold campaign finance bill several years back attempted to keep the influence of money down. Then the Supreme Court ruled in the Citizens United case that, in effect, corporations can donate as much money as they like, and the cost of political campaigns instantly rocketed to another level.

The Swamp spends a fair amount of time recording scenes we might not expect to see these days, like Massie, Buck, and Gaetz smiling and joking rather than snarling. It shows all three engaged in cordial relationships with theoretical mortal enemies over on the progressive left.

Gaetz says at one point that the real divide in American politics today isn't Republican and Democrat as much as it's those who want to reform the big money/lobbying system and those who are happy to ride the wave. Alas, he says, it works so well for so many people on both sides of the aisle that they use it to require an almost military level of intra-party discipline.

Despite the fact Massie is a reliably conservative Republican vote, he drew the wrath of Trump himself earlier this year when he requested a roll call vote on the $2 trillion stimulus package.

With a spending bill of this magnitude, Massie argued, every representative should, at the very least, be required to go on record.

The party leaders didn't want that. Neither did Trump, who told Massie that if he didn't withdraw his request, he could be challenged in the Republican primary.

He lost his roll call bid, acquired a challenger, and says he regrets nothing.

The Swamp is inevitably depressing because it suggests the water level in the real swamp hasn't dropped a millimeter.

But it may give viewers a different perspective, and just focusing the discussion might be a step toward eventually flushing out some of the more lethal wildlife lurking just below the surface.