Having failed to come together on healthcare, Senate Republicans are back to square one: resurfacing a 2015 bill vetoed by former President Barack Obama that would repeal portions of Obamacare but lay no framework for a replacement plan.

It's unclear whether even this bill could pass, now that Republicans worried about going too far in repealing Obamacare or not far enough know President Trump could sign it into law.

The Congressional Budget Office projections for the earlier clean repeal legislation showed significantly higher numbers of uninsured than under the proposals Republicans have been struggling with in recent months. The now-defunct Senate bill would have increased the number of uninsured by 22 million people, but the 2015 bill, the Restoring Americans' Healthcare Freedom Reconciliation Act, would boost the number of uninsured even more, by 32 million over a decade.

Republicans have to contend with a narrower margin than they had in 2015, when they held 54 seats in the upper chamber and the bill passed 52-47. They now hold 52 seats and cannot afford to lose more than two votes, assuming a tie-breaking vote by Vice President Mike Pence.

Republicans who supported a full repeal back in 2015 may not do so again. Chief among them is Sen. Shelley Moore Capito, R-W.Va., who voted for the 2015 bill but hadn't signed on to the most recent Senate healthcare legislation because of severe cuts to Medicaid that were planned for the long term.

Sen. Susan Collins, R-Maine, is expected to vote against the bill because she was one of only two Republicans who voted against it in 2015 and she has said that she wants to work with Democrats to fix Obamacare.

But the idea has a lot of support among hardline conservatives who have complained that the latest bill didn't do enough to repeal Obamacare, including Sens. Rand Paul, R-Ky., and Mike Lee, R-Utah, who came out against the current bill but have said they would welcome full repeal.

The vote, expected to take place this week, was announced Monday by Senate Majority Leader Mitch McConnell, R-Ky., after four Republicans publicly opposed the healthcare bill that had been debated in recent months, the Better Care Reconciliation Act. Republicans cannot afford to lose more than two votes on any healthcare bill because they are advancing it through a measure called reconciliation, which requires a simple majority vote instead of the 60 needed to break a filibuster.

Because they hold only a 52-seat majority, the GOP holdouts including Collins, Paul, Lee and Jerry Moran of Kansas were enough to sink the bill. Though Republicans were given a week longer than they expected to discuss the details of the legislation, McConnell instead announced that it was time to take another route. Ahead of Monday's announcements, deep divisions remained over how to handle the Medicaid program and how to reduce premiums.

The old bill would repeal Obamacare and delay the implementation over the course of two years. It would undo the employer and individual mandates, Obamacare's taxes, and the expansion of Medicaid to low-income people. It does not contain the same long-term changes to Medicaid that would alter the growth rate and result in hundreds of billions of dollars in cuts. The strategy is risky heading into the 2018 elections, as insurers would know that the Obamacare-created exchanges where they sell tax-subsidized plans would soon be undone. Several have already dropped out, and others are seeking to significantly increase premiums.

Still, the approach has been encouraged in recent weeks by President Trump and by Pence.

"Republicans should just REPEAL failing ObamaCare now & work on a new Healthcare Plan that will start from a clean slate. Dems will join in!" Trump tweeted Monday soon after support collapsed for repeal and replace.

Pence agreed with the president, tweeting that Republicans should keep their promises. Other Republicans swiftly called for repealing Obamacare and then working on a replacement in a few years.

Among them was Rep. Mark Meadows, R-N.C., head of the hardline conservative Freedom Caucus.

"Let's put the same thing on President Trump's desk that we put on President Obama's," he tweeted, a reference to the 2015 repeal bill.

Paul also called for repeal and delay soon after the announcements from Lee and Moran. Lee has said he supports the full repeal.

Republicans have been down this road before and have taken a different path. When the new Congress convened back in January, there was talk of repealing Obamacare but leaving it in place for a few years.

The time frame was also longer than in the 2015 repeal bill, which only gave two years for Congress to pass and transition to a new system. But the plans drew concerns over whether Congress can come up with something to replace Obamacare.

Meadows himself called for having a replacement for Obamacare on the same day that it was repealed. He told BlueRidgeNow.com back in February that he favored repealing and replacing the law at the same time.

Paul also called for repeal and replace in a January tweet and had support of Trump.

"I just spoke to @realDonaldTrump and he fully supports my plan to replace Obamacare the same day we repeal it. The time to act is now," he tweeted.

After failing to get enough support for that approach in the Senate, Republicans are now starting all over again.