A donor could also, in theory, give $5,000 per year to every political action committee currently registered with the Federal Election Committee. That would total more than $13 million, versus the $74,600 allowed under the existing aggregate cap.

Party officials have been effectively prohibited from soliciting supersize checks since Congress moved in 2002 to ban unlimited contributions to party committees, also known as “soft money.” The prestige and financial muscle of party leaders was further eroded by the court’s Citizens United decision in 2010, which led to super PACs, which could raise and spend unlimited amounts of money so long as they did not coordinate with parties or candidates. Super PACs have spent more than $700 million since that decision.

But the ruling offers a path for party officials to re-establish themselves as kingmakers. And because senior congressional leaders often have the closest ties to big donors, the decision could give them a tool with which to discipline rank-and-file members.

The decision will go into effect in a matter of weeks, though it could be months before the Federal Election Commission drafts new rules to conform to it.

Supporters of the decision said that it could bring about more transparency to campaign fund-raising, since the new money would flow into entities, like political parties, which are required to disclose their donors. Political nonprofit groups, for example, face no such requirement.

Reince Priebus, the chairman of the Republican National Committee, which joined the lawsuit with Shaun McCutcheon, an Alabama businessman, said, “Today’s court decision in McCutcheon v. F.E.C. is an important first step toward restoring the voice of candidates and party committees and a vindication for all those who support robust, transparent political discourse.”