Texas Land Commissioner Jerry Patterson has endorsed Ryan Sitton for railroad commissioner, Sitton’s campaign said Monday.

That announcement comes three weeks before the Republican runoff election for the seat vacated by Barry Smitherman. Sitton, a Houston oil and gas engineer, faces former state Rep. Wayne Christian in an increasingly contentious race. Christian, of Center, led Sitton by 12 percentage points in the four-way March balloting.

“Ryan’s energy expertise will serve Texas well and ensure that Texas leads the nation to energy independence,” Patterson said in a statement. “Ryan Sitton’s qualifications for railroad commissioner are unmatched.”

Sitton’s other endorsers include Smitherman, former Railroad Commissioner Elizabeth Ames Jones and Becky Berger, who finished behind Christian and Sitton on primary day. Christian has been endorsed by former Railroad Commissioner Victor Carrillo, several Tea Party groups and a coalition of state lawmakers.

Patterson, who did not advance to the runoff in the Republican race for lieutenant governor, has also thrown his weight behind the incumbent in that race, David Dewhurst, who faces state Sen. Dan Patrick, R-Houston, on May 27.