In losing big votes, Senator Chuck Schumer, the New York Democrat and majority leader, believes his party stands to win.

Despite certain defeat, Mr. Schumer has scheduled a floor vote for Thursday on a bipartisan border security measure that collapsed almost as soon as it was made public in February, when Donald J. Trump torpedoed it as “lunacy” and “a gift to Democrats.”

Mr. Schumer sees his maneuver as a way to remind voters upset about chaos at the southern border that it is Republicans who are blocking a solution, even after they reached a deal with Democrats that could solve the problem. He insists that the potential political benefits to Democratic candidates in tough races in Ohio, Montana and elsewhere are merely a bonus.

“It’s good for the country,” Mr. Schumer said in an interview, about the legislation. “But obviously, look, if it has electoral consequences, so be it.”

With most of the heavy legislative lifting done for the year and the election that will decide control of Congress fast approaching, Senate Democrats are turning to the “electoral consequences” part of their agenda, and messaging votes will be a regular feature. Mr. Schumer, who has long played a central role in mapping his party’s political strategy, has a two-pronged plan that will unfold in the coming weeks with a focus on abortion rights and border security.

“In the next two months,” Mr. Schumer said, “we have a sword and shield.”

The sword is abortion rights, an issue where Democrats firmly believe — and polls confirm — they have the upper hand with voters following the Supreme Court ruling that overturned Roe v. Wade.