WASHINGTON — Very little is happening in the Senate these days, but what passes for action has a lot to do with re-electing Democrats — or blocking their re-election.

Senator Kay Hagan, Democrat of North Carolina, saw her popular sportsmen’s bill crash on the Senate floor on Thursday when her Republican co-sponsors flipped, voting instead to filibuster and ensuring that it would die. Next up on the list of legislation with voter appeal but little chance of passage: a contraception access bill sponsored by Senator Mark Udall, Democrat of Colorado, or a measure to end tax breaks for companies that send jobs overseas, offered by Senator John Walsh, Democrat of Montana.

The three Democrats are among the more vulnerable going into Election Day this November. All could use a late accomplishment on legislation drafted for important constituents in their state. Senator Harry Reid of Nevada, the majority leader, has used his powers to selectively give them a platform and the megaphone of the Senate floor. But even that collides with a Republican Senate minority that is united to deny them any victories.

Image Mark Udall Credit... Joshua Roberts/Reuters

Senator Mitch McConnell of Kentucky, the Republican leader, called the Senate floor “a campaign studio for one political party,” and Democratic leaders are not exactly denying that they are giving their endangered senators precious floor time for political reasons. Senator Charles E. Schumer, Democrat of New York, said it was a time-honored bipartisan tactic.