"It is the honor of my life to serve Texas in the U.S. Senate," Cornyn said in a statement on his social media accounts. "Inspired by your trust and your patriotism, I will continue to be a strong voice for our values in Washington."

Cornyn sought to connect Hegar to Democratic plans to rein in fossil fuel production and reform police departments, and he tied her to House Speaker Nancy Pelosi and Senate Minority Leader Chuck Schumer in arguing she wanted to "make Texas more like California and New York."

Hegar was running behind in the polling averages leading up to Election Day, but Democrats closed strong in races throughout the state, including a number of congressional and state legislative battlegrounds. Trump and former Vice President Joe Biden were running neck and neck over the past month.

Hegar got a late boost from online donors, who poured money into her campaign in the final months, and from Senate Majority PAC, which went into Texas late with ads attacking Cornyn on health care.

"We’ve built a powerful grassroots movement from the ground up, and I know our fight here in Texas is far from over," Hegar tweeted Tuesday night.

Neither Trump nor Biden visited Texas during the campaign, although the state saw record early voting turnout. Biden's running mate, Sen. Kamala Harris, traveled there Oct. 30, but Trump and Vice President Mike Pence stayed clear entirely, insisting it wasn't in play. "Texas is not a battleground state," said former Energy Secretary and Texas Gov. Rick Perry.

Cornyn did try to seek some distance from Trump in the latter stages of the campaign, criticizing his rhetorical style before the election. “There’s just not any discipline," Cornyn said. "I mean the president’s got a great record to run on. But we don’t hear too much about it. And I just think that’s a mistake."

Lauren Gardner contributed to this report.