The primary runoff election Tuesday with the greatest statewide implications will be decided by a few thousand Republican voters who live in and around the oil-refining city of Beaumont in Southeast Texas.

That’s home base to embattled House Speaker Dade Phelan, who has been targeted for defeat by some of the most powerful Republican officeholders and donors in Texas, and even by former President Donald Trump. And if the two-term speaker and four-term House member is toppled by political newcomer David Covey, it would touch off a pitched battle for the lower legislative chamber’s top leadership post that could reshape the Texas political landscape for years.

“This is a pretty heavy lift for the voters of that district,” said Brandon Rottinghaus, a University of Houston political science professor. “We rarely see a Texas House speaker in political jeopardy (at home). They typically have got the political ear of their districts, and have got enough power and money to hold on to those seats. We’re seeing that upended in a race that could dramatically change the fate of the next several legislative sessions. That’s not too fine a point to put on it.”

The race for Texas House District 21 stretches south from the East Texas town of Jasper and takes bites out of Beaumont and Port Arthur as it extends to the Gulf Coast. The high-profile runoff, fueled in no small measure by the endorsements of the former president and both Lt. Gov. Dan Patrick and Attorney General Ken Paxton, has attracted millions in political contributions from inside and outside Texas.

With neither party featuring a statewide contest in the runoffs, the GOP primary battle for District 21 has outsized implications because of Phelan’s position as the leader of the 150-member, Republican-dominated House. No Democrat is on the District 21 ballot, so the winner of the GOP runoff will take the seat when the Legislature convenes in January.

More: Texas primary races will be settled soon. A look at the Democratic, Republican runoffs.

And that fact was punctuated during the Texas GOP’s three-day state convention in San Antonio, which began Thursday, as many of the party activists, especially those from its archconservative wing, scarcely missed an opportunity to express their displeasure with Phelan.

State Republican Chairman Matt Rinaldi set the tone in his remarks that opened the convention by faulting the speaker for not ending the House’s decades-long practice of awarding some committee chairmanships to the minority party.

“Last year, House Speaker Dade Phelan handed political power in the Texas House to Democrats,” Rinaldi said. “He went to war with the Texas GOP lieutenant governor in Texas Senate.”

Phelan, meanwhile, is not without allies in his own party. During the run-up to the March 5 primary, former Gov. Rick Perry campaigned for the speaker in his home district. Phelan’s endorsement page on his campaign website lists state Sen. Robert Nichols, an East Texas Republican, along with several dozen local elected officials from the district.

The speaker also touts the backing of the National Rifle Association, the anti-abortion Texas Alliance for Life and such pro-business organizations as Texas Realtors, the Texas Oil and Gas Association, and the Texas Association of Business.

More: Texas Republicans open their convention as they seek to motivate base ahead of election

On social media, Phelan pushed back against intraparty claims that he is in the pocket of House Democrats.

“I have led the two most conservative sessions in Texas history, and I’m ready for a third,” he said Thursday in a post on Instagram. “We passed constitutional carry, banned cities from defunding the police, banned gender modification on kids, cut property taxes by billions, and moved to finish the border wall. It’s time to head to the polls and keep our conservative wins going in Texas.”

Covey, a former Orange County GOP chairman and oil and gas consultant, is playing up his endorsement from Trump, prominently featuring the former president at the top of his campaign website.

“President Trump vocalized his support for my candidacy again at the NRA convention this weekend because he knows I will relentlessly fight the Austin Establishment every day. I have the will to stand up for this community and our values, and that’s exactly what I intend to do,” he said in a recent news release.

Covey won the first round in what started as a three-candidate race, besting Phelan by 3 percentage points but falling short of securing an outright majority to win the GOP nomination in the March 5 primary, which drew about 34,000 Republican District 21 voters to the polls. In the weeks since, Covey has received hundreds of thousands of dollars from the Texans United for a Conservative Majority PAC, founded by oilman and Republican megadonor Tim Dunn. He also received $100,000 from Patrick.

Phelan, meanwhile, has outraised his opponent and recently received about $660,000 from Las Vegas casino owner Miriam Adelson.

Rottinghaus noted the historical implications of Tuesday’s vote in District 21. Sometimes Texas House speakers are ousted because they lose support of the membership or simply choose to retire. But one has not faced the prospect of rejection from his own local voters since 1972, when Rayford Price was defeated in the Democratic primary in the midst of what came to be known as the Sharpstown stock fraud scandal involving financial misdealings that ended several political careers.

“The last time we had a House speaker in serious political jeopardy, there was a major scandal that rocked that party’s leadership,” Rottinghaus said. “So that’s the most interesting thing.”

This article originally appeared on Austin American-Statesman: Texas primary: Will Dade Phelan survive David Covey challenge?