The growing list of Democrats who have signed on to ethics legislation that would ban ownership of individual stocks is remarkably bipartisan, speaking to the political power of the issue. On the Democratic side, the names parallel the party’s list of endangered incumbents, many of whom rushed to sign on after Speaker Nancy Pelosi of California expressed her opposition in December.

“We introduced this in June 2020 and reintroduced it this Congress,” said Representative Abigail Spanberger of Virginia, a Democrat from a politically competitive district who wrote a stock ban with Representative Chip Roy of Texas, a conservative Republican. “We were steadily adding co-sponsors, but it is absolutely the case that the speaker’s answer to that question related to stock ownership and trading really ignited this as an issue.”

The legislation faces a climb on Capitol Hill, where the skepticism of top Democrats makes it unlikely to be considered. Representative Steny H. Hoyer of Maryland, the House majority leader, reiterated his opposition on Wednesday. Ms. Pelosi, after initially dismissing the effort, more recently said she would be open to it if proponents could muster the votes, even as she suggested she considered it a bad idea.