WASHINGTON — Jewish Republicans know they are not many in number. But at a recent gathering at the St. Regis Hotel in downtown Washington, they pondered the meaning of an especially alarming figure: zilch. As in zip, bupkis, zero.

The stinging defeat last month of Eric Cantor, the House majority leader and the highest-ranking Jewish politician in American history, has created the possibility of Republicans having no Jewish representation in the House or Senate for the first time in more than a half-century.

“Sometimes, a Jewish person just wants to be able to go to Congress and speak with a Jewish person,” Beverly Goldstein, a Republican donor from Beachwood, Ohio, explained in the hotel lobby after a meeting of the Republican Jewish Coalition.

“And Chuck Schumer is not it for us,” she added, referring to the Democratic senator from New York.

Excluding the soon-to-be-retired Mr. Cantor, there are now 31 Jewish members of Congress — 30 of them Democrats and an independent senator from Vermont, Bernard Sanders, who generally votes with Democrats.