The Senate is beginning a potentially decisive week in the GOP’s long-running and arduous attempt to roll back the Affordable Care Act. McConnell and other GOP leaders have thus far rejected pleas from several Republican senators for more time to consider and revise the bill released last Thursday; they are determined to finish the bill before Congress breaks for a July 4 recess and are gambling that wavering Republicans will ultimately fall back in line rather than torpedo the party’s top legislative priority in a climactic vote.

“I am closing the door,” Senator John Cornyn, the second-ranking Republican, tweeted on Monday morning after earlier suggesting a vote could wait until July. “We need to do it this week before double digit premium increases are announced for next year.”

In perhaps the most damaging finding for Republicans, the CBO projected that the number of uninsured people would spike by 15 million in a single year if the Senate bill, titled the Better Care Reconciliation Act of 2017, became law. That number would grow to 22 million by 2026. Average premiums would also go up initially before dropping over time. They would be 30 percent lower in 2020 than under current law, the CBO found, and 20 percent lower in 2026.

Republicans can point to more favorable findings from the CBO in other areas. The legislation would reduce the deficit by $321 billion over a decade, as the steep cuts in government spending outweigh the elimination of taxes in Obamacare. That could give GOP leaders breathing room to add money sought by moderates, either to reduce the cuts to Medicaid or to bolster support for states combatting the opioid epidemic. Under Senate budget rules, the legislation cannot add to the deficit over a 10-year window.

As to the broader stability of the insurance market, the CBO saw the Senate bill as having less of an impact than either its critics or defenders have claimed. The budget office wrote that despite rising premiums and GOP assertion’s that Obamacare is “collapsing,” the individual insurance market remains stable in most part of the country. And the Senate bill would do little to change that. But it did warn that after 2019, “a small fraction of the population” would reside in areas where “no insurers would participate in the nongroup market or insurance would be offered only with very high premiums.” The CBO also found that even though average premiums would drop, out-of-pocket costs would rise for many people because plans would cover fewer services and have higher deductibles. “As a result, despite being eligible for premium tax credits, few low-income people would purchase any plan,” the report predicted.

By comparison, the House’s American Health Care Act would have resulted in 23 million fewer people having insurance after a decade, the CBO estimated last month, with a large chunk of those losses resulting from a $834 billion cut to Medicaid. That finding—along with polls showing the bill to be deeply unpopular—prompted Republicans in the Senate to start over and write their own bill to partially repeal and replace the Affordable Care Act. But the CBO on Monday confirmed that the proposal Senate leaders came up with was broadly similar to the House bill.