MJ Hegar wins Democratic Senate runoff, will take on U.S. Sen. John Cornyn

Air Force veteran MJ Hegar won the Democratic nomination in Texas for U.S. Senate on Tuesday night.

Hegar defeated state Sen. Royce West (D-Dallas) in a primary runoff election that had been postponed because of the coronavirus pandemic.

Hegar will be an underdog against Republican incumbent John Cornyn but Democrats believe President Donald Trump's sagging poll numbers give them an opening for an upset in America's biggest red state.

FULL RESULTS: Click here to check Tuesday's election results

Just after 11 p.m., Hegar declared her victory on Twitter thanking Texans.

In a speech to supporters, delivered online due to the pandemic, Hegar said she was ready for the general election in the fall.

"We are going to keep making calls, keep hosting virtual events, keep raising up a grassroots army, because tonight we have a message for John Cornyn and he’s heard it before -- pack it up buttercup, because your time has ended and we are coming to take our seat back," Hegar said.

West conceded on Wednesday morning, thanking his supporters for making the race close and claiming he was outspent by millions of dollars. Despite the loss, he plans to support Hegar in the fall.

"I have been working to elect Democrats for decades, and I look forward to turning Texas blue in November,” West said. 

November's contest will be the biggest re-election test of the three-term Senate veteran's career as Texans grow increasingly upset with Trump's handling of the pandmic and voters could punish fellow Republicans on the ballot. The state GOP is also on alert two years after Republican Sen. Ted Cruz only narrowly held onto to his own seat in Texas. 

Hegar has run as a moderate and nearly won a House seat in a heavily conservative district in 2018. 

The Associated Press contributed to this report.

RELATED: 

Amid growing coronavirus concerns, North Texans head to the polls for primary runoff

Candace Valenzuela defeats Kim Olson in Democratic runoff for Texas US House District 24

North Texas election administrators working to keep polling places sanitized, safe for runoff voting