Voters in Texas head to the polls on Tuesday for the Republican run-off in the highly contentious US Senate primary between the state’s Attorney General Ken Paxton, who was endorsed by President Donald Trump, and John Cornyn, the incumbent, who has represented Texas in the US Senate since 2002.

Whoever wins the runoff will advance to November’s midterm elections, where they will face the Democratic nominee, James Talarico.

Democrats have not held a statewide seat in Texas since 1994, but races have become increasingly tight over the last decade. Paxton, who is the likely Republican nominee, is considered less likely to fare well against Talarico in the general election.

Why is Texas now competitive when it has not been in the past? Al Jazeera analysed why changes could be on the way for Texas in November.

Who are the candidates?

Ken Paxton, 63, is the Republican attorney general of Texas, who was endorsed by Trump in a lengthy post on the president’s social media platform, Truth Social. The longtime Trump ally has been known to take on Big Tech companies, including Facebook in 2022 – for allegedly using Texas biometric data without prior consent – and Netflix earlier this month.

Paxton has also made border security a core part of his platform, saying he wants to finish building Trump’s border wall with Mexico. He has also pledged to cut taxes while investing in cryptocurrency development.

In his endorsement of Paxton, Trump said that the other contender, John Cornyn, was not supportive of him when “times were tough”.

Cornyn, however, has voted with Trump 99 percent of the time and has closely aligned himself with Trump on immigration and border security.

Cornyn, 74, a Houston native, served as the state’s attorney general and as a justice in the Texas Supreme Court before joining the Senate.

Why are Republicans worried about Paxton?

Paxton’s history is riddled with controversy. He has faced allegations involving adultery, securities fraud, and support for the January 6 insurrection, issues political strategists say Democrats could use in attack advertisements during the general election.

“Ken Paxton presents a target-rich environment for Democrats in November: allegations of serial adultery, mortgage fraud, securities fraud, a 7,000 percent increase in net worth while in public office, retaliation against conservative whistleblowers, support for January 6th, and ties to disgraced investor Nate Paul, including using his position as attorney general to benefit him. There’s just so much to work with,” Mark Jones, a professor of political science at Rice University, told Al Jazeera.

Among the most vocal Texas Republicans opposing Paxton is Matt Shaheen, a member of the state’s House of Representatives, who has argued that Paxton would hurt the GOP’s statewide prospects.

“Ken Paxton is the Democrat’s best hope to turn Texas blue!” Shaheen wrote in a post on X.

In another, he said: “Paxton would be toast against Talarico & would get Republicans killed down ballot.”

Shaheen was referencing a poll – commissioned by Texans for a Conservative Majority, a pro-Cornyn super political action committee (PAC), and shared by the Texas Tribune – that suggested that a Paxton nomination could lead to a five-to-eight-point decline for Republicans in down-ballot races. The margin could make safe Republican districts into ones that Democrats could potentially flip.

Shaheen declined Al Jazeera’s request for an interview.

Republicans are also concerned about how the race could affect the balance of power in the US Senate. A Democrat win would be historic, seeing that the state has been held by Republicans since 1994. But it would also get the Democratic Party a step closer to flipping control of the Senate, which, in turn, would give it power to nominate not just Cabinet members, but also heads of government agencies and judges.

Trump’s endorsement of Paxton came amid growing frustration with Senate Republicans after they declined to follow Trump’s calls to fire Senate parliamentarian Elizabeth MacDonough, who had ruled that Republicans could not include funding for Trump’s proposed ballroom project in a budget reconciliation process for immigration enforcement funding.

Senate Majority Leader John Thune had reportedly been lobbying for a Cornyn endorsement.

Citing a senior Republican source, the news outlet NOTUS said Republicans are concerned that Cornyn could have little incentive to support Trump’s agenda for the remainder of his term if defeated, much like Bill Cassidy, who recently lost re-election in Louisiana.

“The next six months could be very difficult for Trump. I think it’s going to be less likely that he gets certain things through,” Renee Cross, senior executive director at the Hobby School of Public Affairs at the University of Houston, told Al Jazeera.

“The average voter is not going to be watching the shenanigans behind the scenes, or maybe on the nightly news, but they are watching the fact that gas prices are up, groceries are up, and we’ve got this war going on that is unpopular with both sides,” Cross said, referring to the US-Israel war on Iran.

Texas is among a handful of states where Republicans could potentially lose control of key seats, along with Maine and North Carolina.

Who will the winner face in November?

The winner of Tuesday’s run-off will face James Talarico, a 37-year-old state representative who defeated US Representative Jasmine Crockett to secure the Democratic nomination in a contentious primary in March. Talarico won 52 percent of the vote.

Talarico rose to prominence as a left-leaning political voice with a religious background. He has been a vocal critic of Christian nationalism, which he described in 2023 as “a cancer on our religion”.

Among his policy proposals are banning stock trading by members of Congress, instituting congressional term limits, and banning presidential pardons.

On cost-of-living issues, he supports raising the federal minimum wage and increasing taxes on corporate stock buybacks.

In foreign affairs, Talarico has voiced support for using US influence to stop human rights abuses against the Uighurs, Rohingya, and Sudanese populations, and to protect Ukraine’s freedom while it faces a Russian invasion, though he has not provided many specifics.

He has been more specific on Israel. He supports cutting weapons funding to Israel, while continuing support for Israel’s Iron Dome missile defence system. He is also an advocate for a two-state solution.

Why is this race different?

In hypothetical matchups, Talarico is either tied with, within the margin of error of, or leading both Republican candidates.

One poll from the Barbara Jordan Public Policy Research and Survey Center showed Talarico tied with Paxton, while Cornyn led him by one point, well within the margin of error.

Other polls show wider Democratic leads. A University of Texas poll showed Talarico leading Paxton by eight points and Cornyn by seven points. Meanwhile, Texas Public Opinion Research had Talarico ahead of Cornyn by three points, and ahead of Paxton by five.

That marks a notable shift from recent Texas Senate races, where Democrats were often competitive but still considered underdogs heading into Election Day.

Texas’s two most competitive recent Senate races both involved Ted Cruz. In 2024, Cruz defeated Colin Allred by roughly 9 points.

In 2018, Beto O’Rourke came closer than the Democrats had in years to defeating Republicans, but ultimately lost to Cruz by 2.6 points.

“People are much more unhappy with the direction of the country than they were in 2018,” Cross said.

“This is certainly a Republican state and a Republican seat, but it could also end up being the perfect storm for Democrats.”

Cornyn’s US Senate seat has historically been less competitive, but the margins have narrowed in recent years.

In this race, Cross says that independent voters could be a make-or-break. A Texas Polling Project survey showed 36 percent of independents backing Talarico over Cornyn, and 39 percent backing him over Paxton, while a large share of independents remained undecided.

“In Texas, independents tend to skew Republican. So if you’re looking at a close race, that could be a major factor here,” Cross added.

“Our movement to take back Texas for working people rises above party politics – because the biggest fight in this country is not left versus right, it’s top versus bottom,” the Talarico campaign said in a post on X, which his campaign pointed to in lieu of a statement.

Neither the Paxton nor Cornyn campaigns responded to Al Jazeera’s request for comment.