7 counties to watch in the runoff between John Cornyn and Ken Paxton

If U.S. Sen. John Cornyn wants to continue his political career, he has to like what he’s seeing in Bell, Travis, Dallas and Williamson counties even before the polls open at 7 a.m. on Tuesday.

In the March 5 primary, Cornyn won all four of those counties by more than 15 percentage points over Attorney General Ken Paxton, and all four are seeing relatively huge turnout in the lead-up to their runoff.

The early voting turnout in those four counties is double the turnout in the last statewide Republican primary runoff, held in Texas in 2022.

Cornyn is facing his toughest primary contest of his 24 years in the U.S. Senate. Paxton, endorsed by President Donald Trump last week, is hoping to become the first challenger to knock off a sitting U.S. senator in a Texas primary since 1970. If Cornyn wins and finishes another term, he would become the longest-serving U.S. senator in Texas history.

Besides the turnout in those four counties, here are three other counties to watch on election day as results start pouring in:

Montgomery County: Just north of Houston, this ruby red county was Paxton’s biggest county during the first round of voting in March. He won 55% of the vote and needs another huge turnout if he’s going to knock out Cornyn. So far, it looks like its happening. More than 30,000 people there have already voted in the GOP primary runoff election. That’s more votes than in all of Travis County, which has double the voter population and has been one of Cornyn’s best counties.

Harris County: This is the jump ball. Cornyn beat Paxton by 1 percentage point in March. But that was also U.S. Rep. Wesley Hunt’s best county. He won 20% of the vote before he was eliminated from the contest. Do Hunt's voters come out again, and if so, for whom? Almost 77,000 people have already voted, crushing past GOP primary runoff elections in Texas. In fact, just the early vote number has now surpassed the entire Harris County vote in 2012, when Ted Cruz defeated former Lt. Gov. David Dewhurst for his term in the U.S. Senate. Cornyn was born in Houston, but neither he nor Paxton has a built-in advantage in the biggest county in Texas.

Bexar County: This is Cornyn’s home base, where he won his first election for a judicial seat in San Antonio in the 1980s. Cornyn only won the county by 4 percentage points in March, but he’s made a big push there ahead of the runoff. Last week, former Gov. Rick Perry, former Sen. Phil Gramm, and former Rep. Henry Bonilla stumped there for him to boost turnout. The 44,000 votes cast in a runoff through Friday are already a record for any statewide Republican runoff election in San Antonio.

A reminder, all 18.7 million Texas voters are eligible to vote in the race, except for the nearly 350,000 people who voted in the Democratic primaries so far. Texas does not register voters by party, allowing any voter to cast a ballot in Tuesday’s GOP primary, as long as they haven’t voted in this year's Democratic primaries.