KATY, Texas — A little more than two months after he dropped out of the race for president, Beto O'Rourke drove 700 miles from his home in El Paso to this city in the vast suburbs west of Houston.

He parked his pickup truck on a residential street on a brisk Saturday morning and started knocking on doors.

Nobody answered at the first home, so he scribbled a note on a campaign flyer and left it on the door. At the next house, a woman cracked open her door just wide enough to grab a brochure from O'Rourke's hand and then made it clear that she wasn't interested in discussing politics. A few houses down, a man answered in his bathrobe.

"Oh, my God, it's Beto O'Rourke," he shouted.

"Yes, sir," O'Rourke said before explaining that he was out campaigning for Eliz Markowitz, a Democrat running for a seat in the Texas House of Representatives in a special election this month. "I was coming by to see if we could count on your vote in this election."

"That's fine," the man said. "But what's your next move?"

"This is it," O'Rourke said before shaking the man's hand and turning toward the next house on his list.

Beto O'Rourke greets Tyler Vaughan, 12, outside a home in Katy, Texas, on Jan. 11. Annie Mulligan / for NBC News

Two years after catapulting to national fame and coming within 3 percentage points of unseating Republican Sen. Ted Cruz — and then failing to parlay the buzz from the campaign into a successful presidential bid — O'Rourke has shifted his attention to a more modest effort: going door to door on behalf of Democrats running for seats in the state House.

"I can't think of a better use of my time," O'Rourke said in an interview this month.

For the first time in two decades, Democrats in what has been the reliably Republican stronghold of Texas believe they have a shot at taking control of the state House in November and, in the process, potentially reshaping Texas politics for years. Republicans hold a narrow eight-seat majority, and whichever party prevails this fall will win an additional prize: a seat at the table, along with the Republican-controlled state Senate, when it comes time to draw new congressional district boundaries after the 2020 census.

"That means that a state that is the most gerrymandered in the union, where it is not the voters that choose their elected leaders, it is the elected officials who choose their voters and do so based on your ethnicity, on your race, on your country of national origin ... that we're going to have fair redistricting in this state moving forward," O'Rourke told hundreds of volunteers who came out to knock on doors in Katy.

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Already, hundreds of thousands of dollars are flowing into Texas from out-of-state donors in an effort to win more than a dozen key races targeted by state Democrats in November. National party leaders are forging similar efforts in other Republican-controlled states, including Florida, North Carolina, Arizona and Georgia. Texas, which has 36 U.S. House seats and the potential to gain as many as three more because of its rapid population growth over the past decade, is viewed as the most important, said Ben Wexler-Waite, communications director of Forward Majority, a Democratic organization that is targeting several Republican-led state legislatures in 2020.

"Up until now, the opportunity to flip the Texas House has mostly flown under the radar, but we've quietly been implementing a long-term plan to finish the job and upend the entire 2021 redistricting process," Wexler-Waite said, outlining his group's plan to spend at least $2.2 million on 20 Republican-held state House seats, most of them in suburban districts outside Houston and Dallas.

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James Dickey, chairman of the Texas Republican Party, said the push to flip the state House reminds him of elections in 2014, 2016 and 2018, when Democrats made a lot of noise about shifting demographics' changing the course of Texas politics — and then went on to lose every statewide race to Republicans, despite making gains in the Legislature.

"I look forward to beating them soundly, as we did then," said Dickey, noting that the GOP is also fielding new candidates in traditionally Democratic-leaning districts with the goal of increasing the Republican majorities in the House and the Senate. "On the other hand, we take very seriously the need to continually earn every Texas voter's support and to remind them that Texas was not the Number 1 state in the country for opportunity and careers prior to the Republican Party taking over the Texas House 17 years ago."

The first test of the Democrats' latest effort comes in the Jan. 28 special election in Fort Bend County, west of Houston. Markowitz, an educator and textbook author, is running against Republican Gary Gates, a real estate investor, to replace state Rep. John Zerwas, a Republican, in a district long considered a GOP stronghold. Early voting begins Jan. 21.