Republican voters in southeastern Texas on Tuesday will settle a bitter primary battle for their party’s future that pits state House Speaker Dade Phelan against conservative activist David Covey, who is backed by former President Donald Trump.

Phelan angered his party’s right flank after he oversaw the impeachment efforts against Texas Attorney General Ken Paxton, who has campaigned on behalf of Covey. Phelan and Covey advanced to a runoff after neither candidate cleared 50% in the initial March primary.

Phelan is the most notable of eight Texas GOP state House lawmakers who were forced into runoffs after nine lost their primaries outright two months ago. Many were also targeted for defeat by Paxton or Republican Gov. Gregg Abbott over opposition to his school voucher program, exposing deep rifts within the party in the traditionally Republican stronghold.

Phelan, who was first elected in 2014 and became speaker in 2021, has perhaps the most politically precarious job in Texas: House speakers must be elected by their districts and 150 members of the Texas House of Representatives. That means a Republican like Phelan must persuade both Democratic colleagues and conservative primary voters in his own district to re-elect him every two years.

His tenuous balancing act in the chamber was upended last year when he oversaw impeachment proceedings against Paxton on corruption charges. The impeachment, and the subsequent trial where he sat with the prosecution, triggered widespread infighting within the Texas GOP and put a target on his back. The state House impeached Paxton, but the state Senate declined to convict and remove him from office.

Paxton, a staunch Trump ally, vowed revenge on those who tried to oust him, campaigning against Phelan and dozens of other GOP incumbents ahead of this year’s primary, while Texas’ old guard — including former Gov. Rick Perry — has come out in support of Phelan.

Approximately $7 million has been spent in the state House district in 2023 and 2024, with Phelan’s campaign spending a whopping $3 million, while Covey’s campaign has spent a little more than half that.

Outside groups have sought to close the gap on Covey’s behalf: The Club for Growth has spent $1.1 million in support of Covey, while the School Freedom Fund has spent more than $376,000 targeting Phelan, who oversaw the House’s defeat of the school voucher program Abbott promoted.

Meanwhile, Trump has kept up the pressure, touting Covey’s candidacy at the National Rifle Association convention in Dallas this month and noting his endorsement on social media.

“David is leading very substantially against your speaker of the House,” Trump said at the NRA gathering. “We have to get your speaker out so we can go into voter fraud.”

If Phelan loses on Tuesday, “it tells you that Trump and [Lt. Gov. Dan] Patrick and Paxton have control of the Republican Party in Texas,” said Cal Jillson, a professor of political science at Southern Methodist University near Dallas.

While Texas’ Legislature had historically prided itself on being capable of bipartisanship, Jillson said Trump’s influence has caused the legislative body to reflect a shift in the party that has happened nationally.

“It really does reflect the broader GOP civil war,” he added. “Texas politics, and the Texas Legislature, is rapidly evolving toward Congress.”

This article was originally published on NBCNews.com