Mr. Olson’s last Democratic challenger, Sri Preston Kulkarni, is running again in 2020.
“Now is not the time to rest,” Mr. Kulkarni, a former diplomat, said in a statement on Thursday. “Now is the time to fight harder than ever. It’s time to ensure that we have leadership in Congress that believes in affordable and high-quality medical care, higher wages for working families, and a fair education system.”
He will face Nyanza Moore, a lawyer, in the Democratic primary, along with other possible challengers. On Twitter, Ms. Moore responded to the news of Mr. Olson’s retirement with a hashtag: “#TakeTheSeat.”
The district is something of a case study for the demographic changes happening in many parts of the country — changes that Democrats hope will open up new paths to victory for them. People of color, who tend to lean Democratic, represent a growing portion of the electorate in states like Texas that have long been reliably Republican, a trend that is especially apparent in Mr. Olson’s district.
Mr. Olson was one of three Republican members of Congress to announce their retirements this week.
Representative Paul Mitchell of Michigan did so on Wednesday, saying in a speech on the House floor: “My objective has always been simply to work to address significant challenges this nation faces: health care, immigration and infrastructure, for example. However, it appears to me that rhetoric overwhelms policy, and politics consumes much of the oxygen in this city.”
And on Friday, Representative Martha Roby of Alabama said that she, too, would leave at the end of her term. Despite voting with President Trump most of the time for the past two and a half years, she had suffered politically for criticizing him in 2016 in response to the Access Hollywood tape that showed him boasting about forcing himself on women.