Four Republican senators, including two vulnerable incumbents who are up for reelection next year, broke ranks Thursday and voted for a three-year extension of enhanced health insurance premium subsidies under the Affordable Care Act (ACA).

The bill needs 25 votes for passage, and a tie would be broken by Republican Lt. Gov. Micah Beckwith, who favors redistricting.

The Senate rejected two health care bills, as the U.S. barrels toward a cliff with steep premium hikes for millions of Americans on Obamacare.