The occasion was his first State of the Union address and the topic was Citizens United, a case the justices had decided in a 5-4 ruling a week earlier, dealing an uppercut to the campaign finance reform movement by ruling that interest groups’ political spending is protected speech under the First Amendment.

The decision rocked politics, and Mr. Obama predicted it would “open the floodgates for special interests, including foreign corporations, to spend without limit in our elections.”

In the first election after the ruling, spending did soar. Cash in congressional races leaped 46 percent and continued to tick up in the years since.

But spending on presidential elections has dropped since the ruling, challenging Mr. Obama prediction of runaway campaigns.

“I think the impact was enormously exaggerated by opponents of the decision right from the beginning,” said lawyer Ted Olson, who argued the case before the Supreme Court on behalf of the plaintiffs.

That was about what Citizens United expected when it went to court in the first place.

In 2008, the conservative group tried to air a documentary critical of Hillary Clinton, who at that time was the favorite to win the Democratic nomination for president.

The group wanted to run ads touting the film and its blockbuster title, “Hillary: The Movie.” At the time, however, federal law prohibited a corporation from airing the ads, deeming them anti-Clinton electioneering subject to the 2002 McCain-Feingold campaign finance restrictions.

“When we first got to the Supreme Court, our main interest was just to show the documentary and some ads,” said Michael Boos, the executive vice president and general counsel of Citizens United.

Conservatives — including President George W. Bush, who signed it into law — believed the courts would declare McCain-Feingold unconstitutional, eliminating its prohibition of corporations using their “general treasury” dollars to fund any “electioneering communications” within 30 days before a primary and 60 days before a general election.

Instead, the courts largely upheld the law, including a 2003 decision by the Supreme Court.

But the retirement of Justice Sandra Day O’Connor, replaced by Justice Samuel A. Alito Jr., ushered in a new era, and the court began suggesting it was open to a rethink.

In 2008, Mr. Obama delivered a jolt to the system by reneging on his pledge to accept public financing for the presidential election. Instead, he became the first major party candidate to tap the exponentially higher sums available outside the public financing limits.

It was a decision The New York Times said “will quite likely transform the landscape of presidential campaigns, injecting hundreds of millions of additional dollars into the race.”

Even after Mr. Obama defeated Mrs. Clinton in the primary race, Citizens United pursued its case, which reached the high court in the spring of 2009.

Just where the justices would come down remained a mystery, as each day passed without a ruling. Mr. Boos said he sat in the court daily wondering what on earth was happening with the famously opaque operations.

He was there in the gallery on the last day of the spring session, too, as Chief Justice John G. Roberts Jr. ran down the last batch of rulings. Only then, Mr. Boos said, did the words “Citizens United” pass his lips, and that was to announce that the court wanted to expand the case and hold a rare second round of oral arguments.

“It was when I heard that I realized we were going to be a major precedent,” Mr. Boos said.

Kagan snared by book ban

When the justices first heard the case, the government was represented by Deputy Solicitor General Malcolm Stewart who, when cornered by Justice Alito, said that under current law, the government could ban books that had pointed political content. Although that answer was correct, it “seemed to take the justice back a bit,” Mr. Boos said. He and Mr. Olson hit that point in briefs before the rehearing.

“When the government of the United States of America claims the authority to ban books because of their political speech, something has gone terribly wrong and it is as sure a sign as any that a return to first principles is in order,” they wrote.

Answering that charge fell to the Obama administration’s new solicitor general, who happened to be Elena Kagan, a longtime legal academic and past dean of Harvard Law School. The rehearing of Citizens United on Sept. 9, 2009, marked the first case of any kind at any level Ms. Kagan had ever argued in public, Mr. Olson said. She tried to walk back the claim about books, but when the justices asked her if pamphlets could perhaps be banned, she said in some cases they could.

“Right then I knew we’d won the case,” Mr. Olson recalled. “I mean, pamphlets? Have you ever heard of Thomas Paine?”

David Bossie, Citizens United’s chairman, remembers the rehearing as a momentous day in every aspect.

“It was a very surreal time for us,” he said. “We’d all been looking at the Supreme Court, wondering what was going to happen, and then here I am sitting across the aisle from Sens. John McCain and Russ Feingold — the guys whose name is on the law we’re trying to overturn. It was a remarkable thing to be sitting right there with them, a who’s who of Washington lawyers, legal writers and members of Congress.”

At first, Mr. Bossie said, he even felt a frisson of sympathy for Ms. Kagan’s lack of courtroom experience — especially when he looked at his legal team, which included, in addition to Mr. Olson, famed First Amendment lawyer Floyd Abrams, who represented Sen. Mitch McConnell, Kentucky Republican.

“She’s obviously a brilliant lawyer but from an experience standpoint, c’mon,” Mr. Bossie said.

The decision came down on Jan. 21, 2010. Justice Anthony M. Kennedy, now bolstered by Justice Alito’s rise to the high court, wrote the 5-4 decision overturning a 1990 precedent and peeling away part of the 2003 ruling that upheld McCain-Feingold.

“Governments are often hostile to speech, but under our law and our tradition it seems stranger than fiction for our Government to make this political speech a crime,” Justice Kennedy wrote.

Obama wrong on foreign money

Six days later, during his maiden State of the Union address, Mr. Obama chided the justices sitting before him, claiming falsely that “even foreign corporations” could now influence U.S. elections. Justice Alito mouthed, “Not true.”

“I thought it was outrageous that Obama did that,” Mr. Olson said.

While disturbed by the false nature of some of the president’s comments, Mr. Olson saw it more as a violation of Washington’s manners. “He was dead wrong about the foreign money — that’s always been illegal and wasn’t a part of the case — but I found the whole thing, him attacking the justices who attend the State of the Union as a courtesy, incredibly rude.”

Mr. Obama said the ruling should not stand, and it became a rallying cry for liberal groups who raise bundles of cash and mount endless petition drives trying to overturn it.

Erwin Chemerinsky, the dean of Boalt Hall, the University of California at Berkeley’s law school, still believes the ruling was in error and said grim predictions have come true.

“What I feared would happen has happened,” Mr. Chemerinski said. “Corporations can and do spend large amounts of money in election campaigns.”

Yet Mr. Chemerinsky said that in addition to the huge totals, the lack of disclosure is equally troubling. Before Citizens United, groups that wanted to run ads in the final days of campaigns had to abide by strict Federal Election Commission rules.

After Citizens United, corporations could use their treasuries — which led to a proliferation of super Political Action Committees, or Super PACs. With no limit on the amount of money that can be contributed to a Super PAC, and with requirements on disclosing donors less stringent than those regarding spending by campaigns or regular PACs, these outside groups have raised enormous sums.

Mr. Chemerinsky argued that leaves the public without the ability to make informed decisions. “I do worry because we should know where it comes from.”

None of the analysts interviewed by The Washington Times believes Citizens United is in any near-term jeopardy. The 2016 election of Donald Trump and his appointment of Justice Neil M. Gorsuch has probably cemented the decision.

“If Hillary Clinton had won, there would be five votes to overturn Citizens United,” Mr. Chemerinsky said. “But she didn’t. Citizens United is secure.”

That opinion is shared by most analysts, including Bradley Smith, a legal scholar and the chairman and founder of the Center for Competitive Politics.

His group was involved with SpeechNow v. FEC, a case that came before the U.S. Court of Appeals for the D.C. Circuit in an en banc hearing right on the heels of Citizens United. The judges there mentioned Citizens United and unanimously ruled that limits on what individuals can give to groups like SpeechNow were unconstitutional.

The two rulings have created a situation in which the really big money to Super PACs has come not from the corporate boards, which have turned out to be averse to having their names attached to partisan politics, but from wealthy individuals.

Even that has proved a smaller role than some believe. Among outside spending in federal elections, the “dark money” whose sources aren’t fully disclosed accounts for a good chunk, but when that is put into the total spending column it amounts to less than 4 percent, Mr. Smith said.

Open Secrets puts conservative groups in a commanding lead among the “dark money” rankings. Although Open Secrets’ top 10 groups are split evenly between liberal and conservative leanings, the top three groups, accounting for more than $550 million since 2008, are conservative.

Still, that money is far less than Mrs. Clinton raised and spent in her 2016 presidential bid. In that race, her campaign topped $1.1 billion, which was essentially twice what candidate Donald Trump spent, even though Mrs. Clinton’s total was less than what Mr. Obama pulled together in 2012, two years after Citizens United.

“There’s been some amount of ‘dark money’ around always, and it can be a pejorative term,” Mr. Smith said. He pointed to the U.S. Chamber of Commerce, one of the biggest players. “Sure, voters may not know every group that contributes to the Chamber of Commerce, but it’s not like, ‘Oh, the Chamber of Commerce! What’s their agenda?’ Voters have a pretty good idea what it is about.

“I think they’ve been good for the system overall,” Mr. Smith concluded of the Citizens United and other rulings. “None of the catastrophe situations opponents wailed would come about have come about, and there have been a lot of competitive races.”

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