WASHINGTON (CNN) -- Money and politics are often equated as the fuel and engine of American democracy, but thanks to the Supreme Court, century-old government speed bumps on the campaign speech superhighway may soon be a thing of the past.

The campaign finance case before the court stems from a film critical of then-presidential candidate Hillary Clinton.

Those are the monumental stakes when the justices return early from its summer recess Wednesday to re-hear a case which could radically alter the election calculus for corporations, unions, advocacy groups, and individuals seeking a voice in the crowded national political debate.

The court will hold a rare special session, which also marks the debut of Justice Sonia Sotomayor. At issue is whether prior rulings limiting corporate spending on federal elections should be overturned. The justices could decide to erase the subtle but important distinction between corporate donors -- which are subject to regulation -- and individual donors, who largely are not.

The potential to upset a long-standing, if shaky, balance over regulating political speech has created a frenzy of cockeyed alliances among groups normally at odds, and spawned nearly four dozen legal briefs.

"It's about money," said Lawrence Noble, former general counsel of the Federal Election Commission and a national expert on campaign spending. "It's about free speech and it's about the ability of corporations to influence elections through the direct use of their Treasury money."

Blame Hillary

The sudden reappearance of campaign finance reform as a major constitutional and political issue can be traced to a documentary on Hillary Clinton. Produced last year by the conservative Citizens United, "Hillary: The Movie" was a scorching attack on the one-time presidential candidate.

The filmmakers wanted to promote it during the heat of the 2008 primary season, but a federal court blocked any ads, as well as airings on cable television's video-on-demand. At the time of the 90-minute movie's premiere, Clinton was locked in a tough primary fight with Barack Obama for the Democratic presidential nomination, but her candidacy failed before the feature was widely shown or had any real impact on the race.

The film later appeared in several theaters, and was released on DVD and the Internet -- outlets that were not subject to federal regulation.

On its Web site, Citizens United promoted its film as featuring 40 interviews -- a "cast to end all casts"-- and promised if "you want to hear about the Clinton scandals of the past and present, you have it here! 'Hillary: The Movie' is the first and last word in what the Clintons want America to forget!"

The group, a Washington-based nonprofit corporation and advocacy organization, balked at campaign finance rules that would have required disclosure of its financial backers, and restrictions on when the film could air. It was financed with a mix of corporate and individual donations.

A special three-judge U.S. District Court panel had earlier rejected the group's arguments the documentary was more akin to news or information programs like PBS' "Nova" or CBS' "60 Minutes."

Section 203 of the comprehensive 2002 McCain-Feingold law bans the broadcast of "electioneering communication" by corporations, unions and advocacy groups if such a broadcast would be aired close to election dates, and would identify candidates by name or image.

The law also requires an on-screen notice of the groups financing such ads, as well as public disclosure of all donors to the sponsoring organizations.

Lawyers representing the FEC urged the justices to subject the ads to the disclosure law, arguing that without it, voters would be "unable to know who's funding the ads."

The Supreme Court initially heard the case in March over how to find balance between, on one hand, Congress' expressed desire to control the power of well-financed private groups to spread their political messages and, on the other, concerns over the First Amendment's guarantee of free speech. The court apparently could not reach a conclusion now on whether independent groups are subject to the same federal oversight as political committees.

"I've seen this movie," Justice Stephen Breyer wryly noted at the time. "It's not a musical comedy."

Re-arguments were ordered, and the scope of the case has now expanded significantly, over whether important precedents banning direct corporate spending in campaigns should be re-examined.

What the court will do

In its most narrow scenario, the five-member conservative majority on the high court appears poised to give the Hillary moviemakers a victory. But that could only be the intermission to a far broader free speech opinion that would benefit other outside groups with a political message they are itching to promote.

During oral arguments in March, questions on the video itself were treated only as the "Coming Attractions" warm-up to larger, substantive discussions on whether federal laws should be scrapped.

A government lawyer defending the FEC flatly declared the government could ban books and Internet expression when those works support or oppose federal candidates in an election year.

Although purely hypothetical since no such law exists, the remarks produced murmurs in the courtroom and skepticism from the bench.

"That's pretty incredible," said Justice Samuel Alito, whose vote could prove crucial in the case. "You think that if a book was published, a campaign biography that was the functional equivalent of express advocacy, that could be banned?"

Chief Justice John Roberts too could be a deciding factor over how narrowly or broadly to toss aside existing regulations.

As for Sotomayor, her record on federal campaign spending is scant, but she is expected to follow in the footsteps of her predecessor. The retired David Souter had consistently backed congressional efforts at spending reform.

The Hillary movie case could launch a range of as-yet unanswered questions about political speech and government regulation.

Since the filmmakers argued their work was information, not political advocacy, should the government place itself as the ultimate arbiter of what is "news"? Some media groups say no. "'Hillary: The Movie does not differ, in any relevant respect, from the critiques of presidential candidates produced throughout the entirety of American history," said the Reporters Committee for Freedom of the Press, in a brief to the high court.

And can distinctions be drawn over regulating quickie 30-second or one-minute "attack ads," and a 90-minute documentary that could be viewed as an ideological "infomercial"?

"McCain-Feingold clearly has an impact on every candidate and everyone that raises or spends campaign dollars," said Edward Lazarus, author of "Closed Chambers," an inside look at the Supreme Court. "And the court has mediated that line between trying to allow Congress to protect against electoral corruption, but at the same time, protect the right of expression of corporations and individuals."

Mind-numbing complexity and bland characters will keep this case from being adapted as a summer blockbuster movie at a theater near you, but its outcome may be keenly felt in future presidential and congressional elections. Whether it produces a happy ending may depend on whether you think election reform deserves a big thumbs up -- or a thumbs down. Either way, the nine justices will be the ultimate critics.

Movie excerpts and the ads can be viewed online at http://www.hillarythemovie.com/.

The case is Citizens United v. FEC (08-205).

All About Federal Election Commission • U.S. Supreme Court