Tuesday’s primary may decide who’s running in the general election — or at least an October runoff — but it will also reveal the effectiveness of the flood of outside money into the races for New York City mayor and City Council.

In the first New York City elections since the U.S. Supreme Court’s 2010 Citizens United decision, which allowed unlimited corporate political spending, the Anybody But Quinn campaign remains the only one dedicated solely to the opposition of a single candidate.

“If she doesn’t win the primary or doesn’t make the runoff, you’re going to be able to attribute it to many factors, but there’s no doubt that this intense negative campaign has had an effect,” said Kenneth Sherrill, a political science professor emeritus at Hunter College.

Two wealthy animal-rights activists and a union boss created the Anybody But Quinn campaign — distinguished by its red T-shirts and vocal presence at campaign events — out of a political action committee named New York City is Not for Sale, which stumped against Mayor Michael Bloomberg during his third election bid in 2009. In the 2013 race, the group started an air war this April, when it released a series of controversial attack ads against Quinn.

“It’s almost like carpet bombing,” Sherrill said. “They started early and they did help to frame her image for people who haven’t followed New York City politics. The speaker of the City Council is an extremely important position, but most New Yorkers have no idea what that office does.”

The Quinn campaign, in turn, accused the ABQ campaign of spreading lies and threatened legal action to block its first ad.

“This is another in a long line of deceptive attack ads, funded by a special-interest group upset that Christine Quinn wasn’t willing to pander to their narrow agenda and pass a bad piece of legislation,” a Quinn campaign spokesman told Newsday in June, referring to a City Council bill that would have banned horse-drawn carriages.

Staffed mainly by animal-rights activists of NYCLASS, a lobbying group seeking to remove horse-drawn carriages from Central Park, the ABQ campaign represents a new kind of political organization poised to replace an atrophying political establishment, Sherrill said.

“It’s maybe the rise of the single-interest and narrow-interest politics, and the demise of patronage and political machines,” Sherrill said.

Scott Levenson, the architect behind the Anybody But Quinn campaign’s advertising and the founder of the Advance Group, a political consulting firm, said the 2013 municipal race will be a point of no return when it comes to outside spending, whose lasting effect would not become apparent until the morning after the primaries.

“Certainly in municipal races,” he said, “2013 will go down as a Rubicon in the introduction of independent spending and the effect it could have.”