Democratic members of the Texas House of Representatives said they’re leaving the state on Sunday, in what would amount to a last-ditch attempt to stop Republicans from adopting an aggressively redrawn congressional map. Their absence would prevent the House from reaching the quorum needed to hold a vote this week.

The move to break quorum was a sharp escalation in the bitter partisan clash over a mid-decade redistricting in Texas that was requested by President Trump. Republicans in the State Legislature were rapidly moving forward, with the map — drawn to flip five Democratic congressional districts to favor Republicans — being passed out of two committees over the weekend.

A floor debate on the map, and a potential vote of the full House, was scheduled for Monday.

The ultimate outcome is far from certain: A walkout by the Democrats’ could delay action in the Legislature for several weeks or more, but comparable past attempts to block Republican legislation and redistricting in Texas have eventually failed.

It was not clear if they were still in Texas on Sunday afternoon or had already left.

This is a developing story. Check back for updates.