One of the surprising things about this year’s Republican presidential race is how long it’s gone on and how competitive and unpredictable it’s been. What’s different this year?

It’s not just the candidates or the political climate. It might just have something to do with the fact that there are more ways for citizens to spend and contribute money to help candidates they like, or to hinder candidates they don’t.

Newt Gingrich, who was pronounced terminal after Iowa, came back to win in South Carolina through strong debate performances — and a big ad campaign by a so-called super PAC, Winning Our Future, that got millions from casino tycoon Sheldon Adelson.

A pro-Mitt Romney super PAC, Restore Our Future, spent some $15 million to help the former Massachusetts governor turn the tables in Florida.

This is all part of the new political landscape that emerged following the Supreme Court’s 2010 ruling in Citizens United v. FEC. The justices held that corporations and unions have a First Amendment right to engage in “electioneering communications.” The super PACs and other advocacy groups have proliferated and prospered because of that decision.

President Barack Obama strongly criticized the verdict, and his campaign said he opposed “unlimited special-interest money” in politics and “favors action — by constitutional amendment, if necessary — to place reasonable limits on all such spending.”

Last week, though, brought word that administration officials will help raise money for a pro-Obama super PAC, Priorities USA Action, to counter the GOP groups. Some of his allies found the president’s change of course disheartening.

But what’s so terrible about the infusion of so much money into the presidential campaign? The political action committees’ main function is one at the heart of democracy: spreading information and arguments that voters may find useful in casting their votes.

The Supreme Court noted in 1976 that “virtually every means of communicating ideas in today’s mass society requires the expenditure of money. . . . The electorate’s increasing dependence on television, radio and other mass media for news and information has made these expensive modes of communication indispensable instruments of effective political speech.” Limits on spending function as restrictions on speech.

No one, after all, has accused super PACs of bribing voters. All the candidates and their supporters can do is get their message out and hope citizens are persuaded.

Critics warn that lavishly funded groups will be able to drown out everyone else, assuring victory for their candidates. But Romney and Gingrich have both proven the limited utility of money.

It enabled them and their allies to get out their messages — about themselves and the other guy — but in last week’s contests, both got their heads handed to them by Rick Santorum. Ron Paul attracts a significant share of voters despite being financially outgunned.

The effort to prevent money from finding its way into the political process has proven itself over and over to be a fool’s errand. Each time laws have been passed to regulate the flow of cash, candidates and advocates have devised methods to get around the rules.

A constitutional amendment to overturn the Supreme Court ruling in Citizens United would amount to an asterisk on the First Amendment — a curb on free speech and free press in the guise of an attack on money. Corporations and unions have a right to communicate because they are collections of individuals joined together for a common purpose. Skeptics would be better off working to focus on ways to foster disclosure and transparency.

Many people find the cacophony of claims and counter-claims this year distracting and disturbing. But raucous and harsh though it might sometimes be, it’s the sound of democracy.