U.S. Vice President-elect Mike Pence (C) joins (L-R) Sen. John Barrasso (R-WY), Sen. John Thune (R-SD), Sen. Roy Blunt (R-MO) and Senate Majority Leader Mitch McConnell (R-KY). Pence talked with the Republican Senators about repealing and replacing Obamacare. (Chip Somodevilla/Getty Images)

After years of promising to repeal the Affordable Care Act, a growing number of Republicans are balking at the prospect of doing so quickly without a firm plan to replace it.

As the Senate begins voting Wednesday on a path to eliminate the landmark health-care bill, some Republicans are worried about the political fallout and uncertainty of starting to roll back Obamacare without knowing how the process will end.

President-elect Donald J. Trump was among the Republicans expressing concern Tuesday.

“I feel that repeal and replace have to be together, for very simply, I think that the Democrats should want to fix Obamacare,” Trump said in an interview with The New York Times. “They cannot live with it, and they have to go together.”

Senate Majority Leader Mitch McConnell (R-Ky.) and House Speaker Paul Ryan (R-Wis.) insisted Tuesday that they have no intention of moving ahead with repeal without a consensus replacement plan. But some Republicans remained concerned about taking a single vote — on a budget measure that sets certain ground rules for what is to follow — before they get through what is likely to be an extremely difficult process of producing an alternative.

Senate Majority Leader Mitch McConnell (R-Ky.) speaks with reporters following a GOP caucus meeting with (L-R) Sen. Corey Gardner (R-Colo.), Sen. John Barrasso (R-Wyo.), Sen. John Thune (R-S.D.) and U.S. Vice President-elect Mike Pence. (Chip Somodevilla/Getty Images)

The chaos focused attention on the political peril Republicans face in seeking to deliver one of their top political promises. Repealing the 2010 health-care law would be certain to have powerful ripple effects for both patients — 20 million of whom have gained coverage through various ACA mechanisms -- and the health-care system as a whole.

The speed with which leaders had hoped to act became part of the problem on Tuesday as Republican leaders considered extending a January 27 deadline for completing a repeal bill. Conversations with Republican senators and a review of their statements show that nearly a dozen have publicly expressed some level of concern about repealing the law without a replacement.

“There are a lot of people that have concerns about doing a repeal with no replacement or at least some guidance on replacement,” said Sen. Bob Corker (R-Tenn.) who has co-sponsored language to delay the nonbinding deadline for repeal legislation until March 3.

“The train leaving the station this week is not a big event, it’s when the train pulls back into the station that’s the big event,” Corker explained.

Sen. Lisa Murkowski (R-Alaska) said that while there is a lot of dissatisfaction on health care among Alaskans, “They at least know what they are dealing with right now.”

She added: “The thought that we would take away what they are seeing now, whether it’s the benefits they are getting from Medicaid expansion, the subsidies they are getting on the individual market ... there is a lot of anxiety and a lot of uncertainty and they are basically asking me: ‘What comes next? We want to know.’”

Such concerns did not appear to jeopardize the frenzied set of procedural votes slated to begin Wednesday known as a “vote-a-rama.” Those votes are an attempt to tinker with a budget measure to establish a process for repealing the health-care law — first by referring it to the relevant committees and culminating in floor votes on actual repeal legislation, probably this spring.

(Daron Taylor/The Washington Post)

McConnell argued Tuesday that Trump’s comments on repeal-and-replace are “not in any way inconsistent with what we’re all aiming for.” But the timeline being pursued by congressional Republicans does not square with Trump’s demand in his interview to vote on repeal as early as next week, highlighting the disconnect between the president-elect and GOP congressional leadership.

“It is difficult for us to sit here and have a serious conversation about repealing and replacing next week,” Sen. Tim Scott (R-S.C.) said Tuesday.

In addition, Trump’s firm commitment to quick replacement legislation is at odds with some Republicans seeking a more gradual process.

“This is going to be a joint effort of the administration, the House and the Senate to put together the replacement. And obviously, we’re going to be talking to [Trump] about how to do that and the people that’s he putting in place that we’re going to confirm will be key players,” said McConnell of Trump.

“In my view we need to cast most of our votes on [replace] before summertime,” said Sen. Lamar Alexander (R-Tenn.), chair of the Health, Education and Labor Committee that will participate in the process. “That will probably take two or three steps and then take two or three years to implement it over time.”

McConnell did not offer specifics about the timing of repeal-and-replace votes while Ryan insisted that full repeal would not happen until Republicans had rallied behind a replacement plan.

“We are going to use every tool at our disposal, through legislation, through regulation to bring replace concurrent with repeal,” Ryan told reporters.

Ryan tried to reassure skittish rank-and-file Republicans Tuesday during a weekly closed-door session by vowing to move swiftly so that some replacement elements can move in tandem with a repeal measure in the coming months.

The Obama administration, meanwhile, continued its efforts to demonstrate that the insurance created under the ACA is popular, despite what officials euphemistically term “headwinds” caused by the law’s uncertain future. Federal health officials on Tuesday released updated enrollment figures, which show that, by Christmas Eve, 11.5 million people had chosen health plans for 2017 through HealthCare.gov and similar marketplaces run by a dozen states.

That is nearly 300,000 more than during the equivalent time a year ago, the officials said. However, the number of people signing up for the first time, about 2 million, is 1 million fewer than last year.

It remains unclear exactly which portions of the law Republicans will seek to dismantle through the budget process. But repeal legislation Republicans pushed through Congress slightly more than a year ago might offer a guide.

Under that bill, vetoed by President Obama, most Americans no longer would be required to carry health insurance or pay a fine, and subsidies would have ended that currently help more than 80 percent of about 10 million people have bought health plans through ACA’s marketplaces.

The previous repeal legislation also would have eliminated an expansion of Medicaid that 31 states have adopted.

All these changes would, in turn, have an impact on insurers, hospitals, and the pharmaceutical industry.

While there is broad GOP consensus about doing away with the law, Republicans do not agree on the shape or timing of a substitute.

“I think people are concerned about is having the flexibility...to deal with things like how do we keep the meltdown on Obamacare from occurring while we’re trying to make the longer-term replacement,” said Senate Majority Whip John Cornyn (R-Texas), the second-ranking Republican.

Cornyn, McConnell and Ryan all insisted they are confident they can craft a replacement that satisfies the majority of their party. But they are likely to need the votes of at least eight Democrats to replace the ACA.

Republican leaders are relying on special budget procedures to repeal portions of the health-care law without the threat of a blockade by Senate Democrats. Senate rules allow budget legislation to be approved with 51 votes rather than the normal 60 needed to pass nearly everything else. There are 52 Republicans in the Senate, ensuring that a unified GOP can act on repeal without Democrats.

But any new health-care legislation would be subject to normal Senate rules and Democrats warn they are not going to rescue Republicans on replacement.

That is exactly what some Senate Republicans are trying to avoid.

“I want to be sure people who are depending on their subsidies or Medicaid expansion are held harmless in this transition,” said Sen. Rob Portman (R-Ohio), who is co-sponsoring the amendment delaying the deadline for writing a repeal bill.

Abby Phillip and David Weigel contributed to this report.