In the election season's first primary of 2018, populists continued to gain ground in their Texas Republican civil war with moderates.

Most of the moderate or establishment Republicans who were targeted in primaries on Tuesday managed to hold on to their seats, but the faction of more populist conservatives, who take a hard line on taxes and social issues, made further advances and could pick up additional seats in May's runoff elections.

"There's been a gradual shift toward the more conservative wing of the party, and that continued in Tuesday's primary," says Brandon Rottinghaus, a political scientist at the University of Houston. "Little by little, they chip away at the support of moderates."

Around the country, there's been a longstanding battle within the GOP over the party's "soul." Different generations of conservatives under banners such as the Tea Party have led insurgent campaigns against old guard Republicans thought to be insufficiently conservative for the times. The party continues to evolve under President Trump.

The results in Texas suggest that the populist wing's power is rising against conservatives who are mainly concerned with issues such as business or education.

Texas has long been firmly under GOP control, with every statewide office held by a Republican. The party currently holds more than 60 percent of the seats in both legislative chambers. But there has been real tension within the party.

Last year, House Speaker Joe Straus blocked several priority bills pushed by Lt. Gov. Dan Patrick and the conservative wing in the state Senate, including an effort to defund Planned Parenthood, a lower cap on local property tax increases and a so-called bathroom bill to regulate use of public facilities by transgender individuals.

Straus didn't seek reelection, but various conservative groups -- such as Empower Texans, Texas Eagle Forum and Texas Right to Life -- sought to oust incumbents associated with him. Their backing from wealthy individuals in the oil and gas industries has erased the traditional financial advantage enjoyed by the establishment wing.

Although 14 of the 21 candidates endorsed by Empower Texans were defeated on Tuesday, they managed to knock off a couple of incumbents and take advantage of open seats to expand the ranks of lawmakers who share their points of view.

"Since the establishment is on the defensive, any loss is significant for them," says Mark P. Jones, a Rice University political scientist. "They're a group that's shrinking, and they didn't add any House seats."

Lt. Gov. Patrick, who easily won nomination to a second term, solidified his dominance in the Senate. State Rep. Patrick Fallon soundly defeated veteran state Sen. Craig Estes, making centrists even more of an endangered species in the chamber. Kel Seliger, who narrowly avoided a runoff by taking 50.5 percent of the vote, will be the last moderate left in the state Senate.

"Everybody else will be in lockstep with Lt. Gov. Patrick," says Jones.

The outcome wasn't as dire for establishment conservatives in the House, where several Straus allies managed to hold on. However, some populist conservatives who were targeted also beat back primary challenges. All told, the Tea Party wing could see a net gain of three to six House seats once the runoff results come in, according to Jones.

Scott Braddock, editor of the Quorum Report, says that the establishment wing of the party could remain strong enough in the House to act as a bulwark against the more conservative Senate. Straus may be out, he says, but someone with his temperament may still take over as speaker.

"The most important vote these members will take in 2019 is for speaker of the House," he says. "That could be someone like Joe Straus who is willing to tell the governor and the lieutenant governor 'no' on occasion."

Not every race came down to loyalty to a particular party wing, says James Riddlesberger, a political scientist at Texas Christian University. For example, moderate GOP Rep. Charlie Geren from Fort Worth, whose brother represented the area in Congress as a Democrat, withstood a well-funded challenge from Bo French, an activist and investor.

"Geren is a well-known candidate and the result may have had more to do with that, rather than whether Empower Texans was behind Bo French," Riddlesberger says.

Gov. Greg Abbott, who trounced two primary opponents on Tuesday to win nomination for a second term, sought to unseat three House Republicans who had questioned the way he raises campaign cash.

Two of them won anyway. The third, state Rep. Wayne Faircloth, lost to Mayes Middleton, an oil businessman who put more than $1 million of his own money into the race.

"I will not be told by anyone in Austin whether I am a Republican," state Rep. Sarah Davis, who was hit with more than $200,000 worth of attack ads sponsored by Abbott, said at her victory celebration. As the sole supporter of abortion rights among House Republicans, she says her win "was about ... the right of a representative to vote her conscience and her district."

It's always dicey for governors to challenge incumbents in primaries. They risk reducing their own stature when they don't prevail. In Abbott's case, the results suggest that while he polls as the most popular politician in the state, that popularity may not be transferable to others.

"If he's going to involve himself in primary fights, he needs to win," says Rottinghaus, the Houston political scientist. "The fact that he lost shows that his political brand is not what he hopes it would be and what a lot of people would assume it would be."

Abbott, who has raised more than $40 million for his reelection campaign, will be a strong favorite over his eventual Democratic challenger. That will be either Lupe Valdez, the former sheriff of Dallas County, or Andrew White, an entrepreneur and son of former Gov. Mark White. The two will square off in a May runoff.

If he wins, Abbott will find himself working with a Senate even more to his liking and a House that may be growing more cooperative.

"The movement conservatives view this not as a single battle but as a war with a long time horizon," says Jones of Rice University. "They never expect to flip 12 or 15 seats in any given cycle. Instead, a net pickup of a few seats means an already weakened establishment is weaker in 2019. Over time, the movement conservative wing [will be] predominant in the House, just like it is now in the Senate."

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