Texas Republicans unveiled a new congressional map Wednesday that creates five additional GOP-leaning districts, in an effort to boost their chances of maintaining control of the House of Representatives as they brace for a challenging midterm election.

Cuellar, a moderate Democrat, is one of two Democrats representing a South Texas district won by Trump last November and is viewed as perhaps the most vulnerable incumbent. Cuellar won reelection by more than five points—but Trump won the former Democratic stronghold by about seven points.