Republican hard-liners in Texas thought this year’s primary elections would be the moment when, after years of trying, they would finally be able to take decisive control of the State Legislature.
They fell just short.
Though more than a dozen Republican incumbents fell to more conservative challengers, the party’s old guard rallied to protect the Texas House speaker, Dade Phelan, from being toppled by an activist endorsed by former President Donald J. Trump.
That victory in a runoff on Tuesday, by a margin of fewer than 400 votes out of more than 25,000 cast, staved off, at least for now, what might have been a swift transformation of the Texas House, which has long been a moderating force in state politics.
How long the House would remain that way was one of the biggest questions emerging from Tuesday’s election. Though Mr. Phelan and a few other high-profile targets avoided defeat this time, the party’s hard right remains confident that its power has yet to peak.
Across Texas, challengers have ousted a total of 15 Republican incumbents from the State House of Representatives in this cycle: Nine fell in primaries in March, and six more in runoffs on Tuesday.
“The party is moving in my direction,” said Representative Steve Toth, a Republican from the Houston suburbs who is aligned with Attorney General Ken Paxton, a leader of the party’s more conservative wing. Mr. Toth spoke on Tuesday outside a polling location in Vidor, Texas, wearing a red “Keep America Great” hat.
But not all the incumbents fell for the same reasons.
Some were targeted because they voted last year to impeach Mr. Paxton on charges of corruption and abuse of office (the State Senate acquitted him). The challengers to those incumbents were mainly backed by Mr. Paxton and Lt. Gov. Dan Patrick, and supported by two influential, religiously conservative billionaires, Tim Dunn and Farris Wilks.
In many other races, the challengers were supported with millions of dollars in campaign spending from school voucher proponents and from Gov. Greg Abbott, a strong supporter of voucher proposals, which would use government funds to help parents pay for private and religious schools.
The governor crisscrossed the state for months to campaign against fellow Republicans who had thwarted his voucher bills during the latest legislative session. On Tuesday, Mr. Abbott claimed victory. “The Texas Legislature now has enough votes to pass school choice,” he said in a statement.
Most of the candidates backed by Mr. Abbott and the Club for Growth, a national conservative anti-tax group, won their races. The group had spent $4.4 million on the Texas House runoff elections alone, including $1.5 million against Mr. Phelan.
“Had he pushed forward with the governor’s school choice bill, none of this challenge would have materialized,” said David McIntosh, the group’s president, referring to Mr. Phelan. “It sends a message around the country that if you’re not for school choice, you’re not a conservative Republican.”
At the same time, there were signs that the Republican Party’s old guard still held sway in some important contests.
Representative Tony Gonzales, a moderate Republican who represents a border district in Congress and was censured by the state party over his votes for gun control and same-sex marriage protections, survived a challenge by about 400 votes out of around 30,000 cast in the runoff.
Craig Goldman, a state representative, easily defeated a Paxton-backed candidate for the Republican nomination in an open congressional seat around Fort Worth, garnering around 63 percent of the vote in the runoff.
Even so, Jeronimo Cortina, a political science professor at the University of Houston, said the results on Tuesday showed that the party was continuing to move to the right. “Absolutely, 100 percent,” he said. “The next Legislature is going to be more uber-partisan.”
The various political currents threatening Republican incumbents this year were often pushing in the same direction. But sometimes they were at odds.
Many of Mr. Paxton’s and Mr. Patrick’s candidates also supported school vouchers, aligning them with both Mr. Abbott and the Club for Growth, a group that has distanced itself from Mr. Trump.
But Mr. Paxton also took on Republicans who tried to impeach him, even if that meant challenging incumbents who were backed by the governor.
For Mr. Patrick, also a supporter of school vouchers, the goal was loftier: to make the relatively moderate Texas House look more like the Senate, which Mr. Patrick leads with a firm, partisan hand.
“This is just one of the battles,” said Derek Ryan, a Republican political consultant. “As far as which direction the party and the state is going, there are more battles to come.”
Mr. Patrick and other hard-line Republicans have strongly objected to the longstanding practice in the Texas House of having members of both the majority and minority parties serve as committee chairs. The hard-liners have attacked Mr. Phelan for continuing the practice, and accused him of mollifying Democratic members in order to gain their support for his speakership.
On Tuesday, Mr. Paxton took that accusation further, saying that Mr. Phelan had taken advantage of the open primary system in Texas to court Democratic voters.
Mr. Phelan said as the runoff was winding down that his campaign was bolstered by the arrival of the old guard, including former Gov. Rick Perry, who came to Mr. Phelan’s aid when it appeared that he might lose.
The Phelan campaign ended up spending more than $12 million to defend his seat in a southeast Texas district that runs from Beaumont to the border with Louisiana, according to filings through mid-May.
In an interview as he campaigned for Mr. Phelan this month in China, Texas, Mr. Perry said he tried to focus his message on the interests of local voters. “I look at politics through the prism of economics,” he said.
Mr. Phelan’s seat in the Texas House may now be safe — his district is heavily Republican — but his speakership could be in doubt. Minutes after the results of the runoff became clear, Mr. Paxton issued a statement warning Republican members against supporting Mr. Phelan for speaker in the next term.
“Ask your 15 colleagues who lost re-election how they feel about their decision now,” Mr. Paxton wrote. “You will not return if you vote for Dade Phelan again!”
The victories by so many challengers may mean that the next legislative session, the 89th in the state’s history, will be one of Texas’ most conservative. Or it may be one of its most chaotic, as the mixed results in the runoffs further inflame the intraparty struggle for control.
Nate Schatzline, a Republican state representative aligned with Mr. Paxton, suggested as much on social media on Tuesday night: “The 89th is about to be wild!”