Four-term Republican US senator John Cornyn is fighting for his political life against Texas attorney general Ken Paxton, in a bitter primary contest that will likely end in a runoff.

As polls began to close across the Lone Star state on Tuesday evening, national Republicans were openly fretting that a victory by Paxton, a scandal-plagued conservative culture warrior who is a darling of Donald Trump’s Maga movement, would give Democrats a rare opening in a solidly red state.

Republicans, including the National Republican Senatorial Committee, have already spent tens of millions of dollars rallying to Cornyn’s defense. Donors will likely be pressed to spend millions more if the race is forced into a 10-week runoff.

Trump has so far not weighed in, heaping praise on all three candidates during a visit to Texas last week. All have touted their closeness to the president, with Cornyn highlighting his record of voting for the president’s agenda. In the last few weeks, he’s also touted his electability, warning that his rival would jeopardize Republicans’ chances of holding the seat in November.

But Paxton has survived years of legal, political and ethics scandals, including being impeached by the Republican-controlled Texas House on charges of bribery, abuse of public trust and obstruction of justice. In the Senate, the vote fell short of the two-thirds majority needed for conviction.

Paxton has led in most polls and appears poised to end Cornyn’s 24-year Senate career. The outstanding question, many observers believe, is not whether he will win, but whether he will win outright, by capturing more than 50% in a contest that also includes rightwing representative Wesley Hunt.

“If you all will please just get out and tell your friends, drag them to the polls and let’s get this over with on Tuesday,” Paxton told supporters in Waco. “Let’s do this without a runoff.”

Even as Trump’s approval ratings falter, and voters sour on his handling of the economy and immigration, Texas Republicans have remained fiercely loyal to the president. In 2024, Trump won the state by nearly 14 percentage points, improving his margins with a boost from Latino voters.

In an interview with CBS, Cornyn conceded that it would be “a challenge” if “only the most radical people” vote in the Texas Republican primary.

Washington Republicans have warned that Paxton would force the party to divert resources away from other key Senate contests to protect a seat long viewed as safely red.

“Honestly, if you look at the polling in a general election setting, I don’t think it’s outside the realm of possibility that the seat [flips], depending on who the Democrats nominate,” the Senate majority leader John Thune told Politico in a recent interview.