In May, Harry Reid, the Senate majority leader, was furious at yet another obstructionist filibuster by Senate Republicans. He admitted then that he was wrong in 2011 not to change the Senate’s rules when he had a chance.

“These two young, fine senators said it was time to change the rules of the Senate, and we didn’t,” he said, referring to Tom Udall of New Mexico and Jeff Merkley of Oregon, who came up with a plan to reduce filibuster abuse that he rejected. “They were right. The rest of us were wrong, or most of us, anyway. What a shame.”

It was a shame, a missed opportunity that helped give Republicans a big cudgel over the last two years. But now Mr. Reid has a chance to rectify that mistake. In January, at the beginning of the next session of the United States Senate, Democrats can vastly improve the efficiency of Congress and reduce filibuster abuse with a simple-majority vote. This time they need to seize the moment.

The filibuster’s importance is as a last-ditch ploy to prevent a minority party from being steamrolled on the most pressing national issues. It was never intended to routinely require a 60-vote supermajority on virtually every issue the Senate takes up. Yet that’s how Republicans have used it in the last six years, to a far greater extent than Democrats ever did when they were in the minority.