It’s surprising that the Gateway Film Center isn’t screening Citizen Koch as part of its Nightmares on High Street series. If your politics are anywhere to the left of, say, Antonin Scalia’s, the documentary is as scary as any horror flick.

The title alone should bring shivers to those who see the PAC-funding Koch brothers as all-powerful manipulators of public opinion. Some even blame them for the recent defeat of the Columbus Zoo levy, thanks to misleading information put out their organization, Americans for Prosperity.

Well, maybe they’re not that powerful. Post-election analysis shows that voters had many problems with the levy, even if they weren’t dumb enough to fall for the group’s propaganda.

But filmmakers Carl Deal and Tia Lessin demonstrate that the Kochs and other deep-pocketed conservatives do pack a formidable punch. And it’s gotten even more formidable thanks to the Supreme Court’s 2010 Citizens United ruling, which made it possible for wealthy individuals, corporations and other organizations to contribute essentially unlimited amounts of money to the task of shaping public opinion.

The documentary begins by examining the decision itself, which overturned decades of court precedent on the issue of campaign finance. The way it came about was equally unusual, we’re told, as the justices seemed eager to make their ruling as expansive and all-encompassing as possible, which was the exact opposite of their usual practice.

Speaking of Scalia, the film suggests that both he and fellow Justice Clarence Thomas had conflicts of interest and should have recused themselves, but they didn’t. If they had, the ruling’s supporters would have lost their 5-4 majority.

However the Citizens United decision came about, its effects were immediate. According to the documentary, it encouraged the growth of the tea party movement and led to conservative initiatives in various states.

From this point on, the documentary focuses mainly on Wisconsin and the union-busting efforts of Gov. Scott Walker and Republican legislators.

Why were Scott and his counterparts in other states out to gut the unions? Because, the filmmakers charge, conservatives wanted to undermine their ability to fund liberal candidates, thus assuring that right-wing candidates and causes would have a near monopoly on the big campaign bucks.

Are you getting scared yet?

Citizen Koch’s biggest weakness is that it spends so much time on Wisconsin politics, including the 2012 effort to recall Walker. We meet some interesting Walker opponents along the way, but it’s hard to become invested in their campaign because we already know how it came out. (Hint: Walker is still in office.)

The doc’s second biggest weakness is that, despite the title, Charles and David Koch appear only briefly. The main focus is on the political movement they represent rather than the brothers themselves.

That doesn’t mean the filmmakers underestimate their influence. A postscript notes that (1) PBS originally planned to air the film but changed its mind, and (2) David Koch is a PBS contributor.

Rating: 3 stars (out of 5)

Citizen Koch, unrated, opens Friday (June 20) at the Gateway Film Center in Columbus.