But the point of the narrow repeal measure would not be to enact it. Instead, Republicans are simply trying to get some measure to bring to negotiations with the House.
“I think people would look at it not necessarily based on its content, but as a forcing mechanism to cause the two sides of the building to try to solve it together,” said Senator Bob Corker, Republican of Tennessee.
Senator Chuck Schumer of New York, the Democratic leader, called that “a ruse to get to full repeal” and warned that hard-line Republicans in the House would apply pressure to reluctant moderate Republicans in the Senate.
A scaled-down bill would fall far short of what Senate leaders had aspired to pass. But if 50 senators could agree, with Vice President Mike Pence breaking any tie, such a bill would at least keep alive the party’s effort to repeal the Affordable Care Act, under which about 20 million people have gained coverage.
“What we need to do in the Senate is figure out what the lowest common denominator is — what gets us to 50 votes so that we can move forward on health care reform legislation,” Tom Price, the secretary of health and human services, said on CNBC.
That strategy would require conservatives like Mr. Paul and Senators Ted Cruz of Texas and Mike Lee of Utah to vote for a measure that leaves the basic structure of the Affordable Care Act in place, hoping that House-Senate negotiations could produce a more ambitious repeal. Such senators have argued that far broader replacement bills did too little to eradicate the health law.
And cracks are already showing.
“The skinny plan is not a replacement of Obamacare,” Senator Lindsey Graham, Republican of South Carolina, said. “Would it be better than Obamacare? Yeah. But that’s not the goal. The goal is to replace Obamacare.”
The Blue Cross Blue Shield Association, a major trade group, warned senators on Wednesday about the possible consequences of repealing the mandate that most people have health coverage. “A system that allows people to purchase coverage only when they need it drives up costs for everyone,” the association said.
With two legislative approaches having been rejected by Republicans — the comprehensive measure and then the repeal-only measure — Democrats were left wondering what exactly Republican leaders were cooking up, and how they could reasonably expect senators to vote on that legislation in just a day or two. Republican leaders have been plotting strategy and drafting legislation largely behind closed doors, with a final vote likely by Friday.
Republicans are seeking topass a repeal bill under special budget rules that limit debate to 20 hours and preclude a Democratic filibuster.
Senate Republican leaders, including the majority leader, Mitch McConnell of Kentucky, have emphasized that senators would be free to offer any amendments they see fit. But Senator Ben Cardin, Democrat of Maryland, highlighted a major challenge that he and other senators face: How can they prepare amendments to legislation without knowing what they are amending?
“What is the bill that we are considering?” he asked. “It’s not the bill that Senator McConnell brought forward because that bill was defeated. It’s not the ‘repeal and we’re starting from a blank slate’ because that was defeated.”
Just a week ago, Mr. McConnell seemed to have failed in putting together a health bill that could pass the Senate. But he managed to persuade enough of his reluctant members to agree on Tuesday to vote for a procedural motion to take up the repeal bill that passed the House in May, and on Wednesday, he vowed to press forward with the repeal effort.
The vote on the repeal-only measure showed the changing political dynamics that Republicans have grappled with this year on health care. With Mr. Obama in the White House, they could pummel his health law, with their words and with their votes, but his veto pen still loomed.
The Senate passed a similar repeal-only bill in 2015, and only one current Republican senator, Susan Collins of Maine, voted against it at the time. But that measure was vetoed by Mr. Obama, while senators are now trying to pass a bill that will actually become law.
But the Congressional Budget Office said last week that the repeal-only legislation would increase the number of people who are uninsured by 17 million next year and by 32 million in 2026 compared with current law.
Senator Lamar Alexander of Tennessee, the chairman of the Senate health committee, was among the Republican senators who voted against the measure on Wednesday. He said he did not believe his constituents would like the idea of “canceling insurance” for millions of Americans and then “trusting Congress to find a replacement in two years.”
“Pilots like to know where they’re going to land when they take off,” Mr. Alexander said, “and we should too.”