The Supreme Court on Wednesday continued its consistent and methodical deregulation of election spending by striking down aggregate limits on federal campaign contributions. The ruling, issued near the start of a campaign season, will change and very likely increase the already large role money plays in American politics.

The 5-to-4 decision, with the court’s more conservative members in the majority, echoed Citizens United, the 2010 decision that struck down limits on independent campaign spending by corporations and unions. Wednesday’s decision concerned the other main pillar of campaign finance regulation: limits on direct contributions from individuals to candidates and parties.

The court’s 88-page decision reflected sharply different visions of the meaning of the First Amendment and the role of government in regulating elections, with the majority deeply skeptical of government efforts to control participation in politics, and the minority saying that such oversight was needed to ensure a functioning democracy.

Chief Justice John Roberts, writing for four justices in the controlling opinion, said the overall limits could not survive First Amendment scrutiny. "There is no right in our democracy more basic," he wrote, "than the right to participate in electing our political leaders."

In a rare oral dissent from the bench, signaling the depth of disagreement between the two sides, Justice Stephen Breyer called the majority opinion a disturbing development that raised the overall contribution ceiling to "the number infinity."

"If the court in Citizens United opened a door," he said, "today’s decision may well open a floodgate."

Wednesday’s decision did not affect familiar base limits on contributions from individuals to candidates, currently $2,600 per candidate in primary and general elections. But it said that overall limits of $48,600 on individuals every two years for contributions to all federal candidates violated the First Amendment, as did separate aggregate limits on contributions to political party committees, currently $74,600.

In his written opinion,Breyer said Wednesday’s decision would allow "a single individual to contribute millions of dollars to a political party or to a candidate’s campaign." He was joined by Justices Ruth Bader Ginsburg, Sonia Sotomayor and Elena Kagan.

The case, McCutcheon v. Federal Election Commission, was brought by Shaun McCutcheon, an Alabama businessman, and the Republican National Committee. McCutcheon, who had contributed a total of some $33,000 to 16 candidates for federal office in the 2012 election cycle, said he had wanted to give $1,776 each to 12 more but was stopped by the overall cap. The party committee said it wanted to receive contributions above the legal limit.

In an interview last fall, McCutcheon said his goal was to encourage the adoption of conservative principles. "To me," he said, "being a conservative means smaller government and more freedom."

Roberts said the core purpose of the First Amendment was to protect political speech from government interference, even if many people might welcome it.

"They would be delighted to see fewer television commercials touting a candidate’s accomplishments or disparaging an opponent’s character," he wrote. "Money in politics may at times seem repugnant to some, but so, too, does much of what the First Amendment vigorously protects. If the First Amendment protects flag burning, funeral protests and Nazi parades — despite the profound offense such spectacles cause — it surely protects political campaign speech despite popular opposition."

Wednesday’s decision seemed to alter campaign finance law in subtle but important ways, notably by limiting the kinds of justifications the government can offer for limiting contributions. Leveling the playing field, Roberts said, is not an acceptable interest. Nor is "the possibility that an individual who spends large sums may garner ‘influence over or access to’ elected officials or political parties," he added, quoting Citizens United.

The only acceptable justification, he said, was rooting out "quid pro quo corruption" or the appearance of it.

Breyer said that analysis was much too narrow. "The anticorruption interest that drives Congress to regulate campaign contributions is a far broader, more important interest than the plurality acknowledges," he wrote. "It is an interest in maintaining the integrity of our public governmental institutions."

"Where enough money calls the tune," he wrote, "the general public will not be heard."

Wednesday’s decision concerned only contributions from individuals. Federal law continues to ban direct contributions by corporations and unions, though they remain free to spend unlimited sums through "super PACs" and similar vehicles.