Four House Republicans broke with party leadership to join Democrats on a discharge petition, securing the 218 signatures needed to force a vote on a three-year extension of enhanced Obamacare subsidies set to expire Dec. 31.

If the subsidies lapse, insurance premiums are expected to double on average for about 22 million people who rely on Affordable Care Act marketplace coverage.

The move highlights divisions within the GOP, as most Republicans favor letting the subsidies expire while a small centrist bloc wants to prevent sharp premium hikes.

House Speaker Mike Johnson opposed the extension and instead advanced a separate GOP health care bill, while the ACA funding measure is unlikely to reach the floor before the deadline, NBC News has reported.

Even if it passes the House in January, the extension faces resistance in the Senate, where Republicans have already rejected it.