Senate Democrats are sticking to their guns, turning back another proposed House amendment to their stopgap spending measure.

Less than an hour after the House voted and fewer than three hours from a probable midnight government shutdown, the message from the Democrats remained the same: Speaker John A. Boehner, R-Ohio, must allow a “clean” continuing resolution to receive a vote on the House floor.

The Senate tabled, and thus killed, the latest offering, 54-46, on a largely party-line vote.

The newest House proposal would delay implementation of the individual mandate under the 2010 health care overhaul and block employer contributions to health insurance on the new Obamacare exchanges. But Democrats have repeatedly said they will not agree to any efforts to undermine the president’s signature legislative achievement, particularly when exchanges created by the law are scheduled to open Tuesday.

Majority Leader Harry Reid, D-Nev., appeared on the Senate floor just after the House gavel banged on the 228-201 vote, criticizing the latest House vote. He took particular aim at a provision that’s come to be named for GOP Sen. David Vitter of Louisiana, calling it “mean-spirited.”

“The House once again has attached ridiculous policy riders that are dead on arrival over here. I’ve heard this story before, in fact just six hours ago,” Reid said in reference to the Senate vote shortly after 2 p.m. today.

Democratic speakers in the last hour included Senate Budget Chairwoman Patty Murray of Washington and Appropriations Chairwoman Barbara A. Mikulski of Maryland.

“Unfortunately … it seems that House Republicans haven’t had quite enough yet. They seem to think this is a game — that whoever is left holding the hot potato will be held responsible. But let me be very clear: The American people are smarter than that,” Murray said. “So I would like to call on Speaker Boehner to take one simple step. I ask that he allow a vote on the Senate’s clean continuing resolution.”