Sen. Mike Lee. AP

Two Republican senators effectively issued a deathblow to the latest Senate GOP healthcare legislation on Monday night, throwing into doubt the future of the Republican effort to repeal and replace the Affordable Care Act.

Sens. Jerry Moran of Kansas and Mike Lee of Utah announced Monday evening that they would vote against a motion to proceed to debate on the bill.

Senate Majority Leader Mitch McConnell had sought to hold a vote this week, but the plan was delayed in part because Sen. John McCain was recovering from surgery to remove a blood clot. McCain's recovery was expected to push the vote back at least a week.

McConnell could afford to lose only two senators and still have the bill move on. Two other GOP lawmakers — Sens. Rand Paul of Kentucky and Susan Collins of Maine — had already expressed their opposition, bringing the total to four.

In a statement, Moran criticized the secretive process used to draft the bill and the fact it could roll back protections for people with preexisting conditions.

"We must now start fresh with an open legislative process to develop innovative solutions that provide greater personal choice, protections for preexisting conditions, increased access, and lower overall costs for Kansans," Moran said.

Lee, on the other hand, said the bill did not do enough to roll back regulations from the ACA, the law better known as Obamacare. The Utah lawmaker supported an amendment introduced by Sen. Ted Cruz that would have allowed insurers to sell plans that did not adhere to two major Obamacare rules.

"In addition to not repealing all of the Obamacare taxes, it doesn’t go far enough in lowering premiums for middle-class families; nor does it create enough free space from the most costly Obamacare regulations," Lee said in a statement.

McConnell admitted defeat in a statement he released Monday night:

"Regretfully, it is now apparent that the effort to repeal and immediately replace the failure of Obamacare will not be successful.

"So, in the coming days, the Senate will vote to take up the House bill with the first amendment in order being what a majority of the Senate has already supported in 2015 and that was vetoed by then-President Obama: a repeal of Obamacare with a two-year delay to provide for a stable transition period to a patient-centered healthcare system that gives Americans access to quality, affordable care."

Senate Minority Leader Chuck Schumer also said he was willing to work with Republicans on a bipartisan approach:

"This second failure of Trumpcare is proof positive that the core of this bill is unworkable. Rather than repeating the same failed, partisan process yet again, Republicans should start from scratch and work with Democrats on a bill that lowers premiums, provides long-term stability to the markets, and improves our healthcare system."

The Better Care Reconciliation Act was on the verge of collapse earlier Monday, but no one wanted to be the deciding vote to kill the bill, as evidenced by Moran and Lee's releasing their statements at the same time.

Reactions came in quickly Monday, with President Donald Trump tweeting that Republicans should pass a simple repeal of Obamacare and work on a replacement later.

Donald Trump. Mark Wilson/Getty Images

"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.

"It's time for a new approach when it comes to #RepealandReplace of Obamacare," Sen. Lindsey Graham of South Carolina, who has introduced his own healthcare legislation, said Monday night.

McCain also issued a statement saying Republicans should restart their attempts on healthcare using a transparent, bipartisan process.

"The Congress must now return to regular order, hold hearings, receive input from members of both parties, and heed the recommendations of our nation's governors so that we can produce a bill that finally provides Americans with access to quality and affordable healthcare," McCain said.

Now that there are enough public votes to block the bill, a wave of moderates who were against the original version of the BCRA may emerge to come out against the newly updated bill, according to Rick Weissenstein at the Cowen Washington Research Group.

"Over the next several days, one of two things is likely," Weissenstein said in a note to clients on Monday. "Either McConnell finds a way to bring Moran and Lee back into the fold or several more Senators join the 'NOs' and McConnell is forced to pull the bill. At this point the later scenario seems more likely and we are now ready to join our colleague Chris Krueger in saying we think the bill is unlikely to pass."

Another big issue for undecided lawmakers had been the release of the Congressional Budget Office's score for the updated BCRA. The original score, which estimated that 22 million more Americans would be without health insurance in 2026 under the BCRA than under the current system, was a key point of contention for centrist Republicans who opposed the first iteration of the healthcare bill.

The new score was originally set to be released Monday, but, given the delay for the vote, it was also pushed back. It's unclear when it will be released, but reports suggest it could be as late as next week.