State Rep. Dennis Paul, R-Houston, announced Thursday he is running for the seat being vacated by state Sen. Mayes Middleton, who is forgoing reelection to run for attorney general.

Paul’s announcement was quickly followed by an endorsement from Lt. Gov. Dan Patrick, the Senate’s powerful presiding officer. Patrick routinely gives his early stamp of approval to GOP Senate candidates running for vacant districts, sending a message to donors and other would-be candidates and, in turn, ensuring the chamber is filled with his political allies.

Paul, a 64-year-old engineer who has served in the House since 2015, said in a statement that he would “remain focused” on the ongoing legislative session but wanted to “make my intentions clear.”

He is the first candidate out of the gate to succeed Middleton, a Republican who represents a slice of southeast Texas running from Galveston to the outskirts of Houston and east Harris County. Virtually all of Paul’s House District 129 overlaps with the north part of Middleton’s Senate District 11.

If elected to the Senate, Paul said, “I will faithfully represent those values which make Texas the greatest state to live, work and raise a family: faith in God; love for family and liberty.”

Patrick said Paul “has everything that’s needed to be a Texas Senator,” citing his “track record of being a stalwart conservative” and his experience in the House.

The domino effect was set off by Attorney General Ken Paxton’s decision to challenge U.S. Sen. John Cornyn in next year’s primary, opening up Paxton’s statewide post for the first time since 2014. Paul’s bid for the state Senate means there will also be an open race for his Republican-leaning House district.

In the decade he has served in the lower chamber, Paul has largely voted as a mainstream Republican, falling toward neither the moderate nor the most conservative end of the spectrum. He has served on the House Insurance Committee in each of his six terms and has been vice chair of several committees, currently serving as vice chair of the Subcommittee on Transportation Funding.