Under attack from the right, House Speaker Dade Phelan and his allies are outpacing their primary opponents in fundraising going into a heated May 28 runoff that’s pitting Republican incumbents against far-right challengers.

The incumbents saw key support from politically connected business groups and megadonors in recent weeks — capped by a surprise last-minute influx from Miriam Adelson, the owner of the Las Vegas Sands casino empire who is intent on legalizing her business in Texas.

Phelan, R-Beaumont, was pushed into an overtime contest after he finished second to GOP activist David Covey in a three-way March primary.