WASHINGTON – Call it the other "Beto effect".

Just months after Democrat Beto O'Rourke outperformed expectations by coming within three points of defeating Republican U.S. Sen. Ted Cruz, Texas Democrats are lining up to run against the state's other U.S. senator, John Cornyn, in 2020.

The latest possible contender is veteran and 2018 congressional candidate Joseph Kopser, who lost to Republican Chip Roy for an open seat previously held by U.S. Rep. Lamar Smith, R-San Antonio.

"Everything's on the table for me," Kopser said in a Wednesday phone interview with the Tribune.

Kopser spoke admiringly of Cornyn but said he was still considering a run against the state's senior senator.

"He's a guy I respect," Kopser said. "But also, I think if you've been in Washington too long, you need to come home."

It's been a dizzying week in posturing for the Democratic nomination as some of the party's most well-known names in Texas have been bandied about and national Democrats have hinted that the race is one they are watching closely. In recent days, U.S. Rep. Joaquin Castro of San Antonio and former state Sen. Wendy Davis openly mulled runs. Veteran and 2018 congressional candidate M.J. Hegar met with U.S. Senate Minority Leader Charles Schumer in New York over the weekend.

Furthermore, Democrat Sema Hernandez, who came in second behind O'Rourke in last year's Democratic primary to challenge Cruz, is also an announced candidate against Cornyn this cycle. She got attention in the primary for drawing more voters than O'Rourke in dozens of counties.

All of the interest in running against Cornyn is a striking contrast to two years ago, when multiple Democrats passed on challenging Cruz, leaving O'Rourke as the most prominent name in the primary.

Along with looking at challenging Cornyn, both Hegar and Kopser are also debating whether to run in U.S. House rematches in 2020. Both ran in GOP-leaning districts yet came within three points of defeating their Republican opponents, U.S. Reps. John Carter, R-Round Rock, and Roy, respectively.

As for Cornyn, he shrugged off all of the posturing in a conference call with reporters Wednesday afternoon.

"It’s a growing list," Cornyn said. "It’s a free country, so anybody who wants to run is welcome to run."

Asked about the prospect of specifically Davis or Castro challenging him, he said, "I'm not very nervous."

Patrick Svitek contributed to this report.

Disclosure: Joseph Kopser has been a financial supporter of The Texas Tribune, a nonprofit, nonpartisan news organization that is funded in part by donations from members, foundations and corporate sponsors. Financial supporters play no role in the Tribune's journalism. Find a complete list of them here.