McCALLA, Ala. — The Supreme Court’s Citizens United decision reshaped American politics by striking down limits on independent campaign spending by corporations and unions. But it did nothing to disturb the other main form of campaign finance regulation: caps on individuals’ direct contributions to candidates.

Shaun McCutcheon wants to change that. He has built a thriving engineering firm here, and he wants to give some of the money he makes to conservative political candidates. But a federal law limits the overall amount he can contribute to all candidates in an election cycle, and that does not sit right with him.

“I think we need to spend more money on politics, not less,” he said. “I think we need to improve it.”

The Supreme Court will hear his challenge to the overall limits next Tuesday. Some critics of Citizens United say the new case, McCutcheon v. Federal Election Commission, No. 12-536, has the potential to destroy what is left of federal campaign finance regulation.