An onslaught of spending and national attention has led to unprecedented voter turnout for a special runoff election in Fort Bend County where both parties are vying for a win that could forecast whether Texas is ripe for a shift in political power.

Cameos from busy presidential hopefuls and hundreds of thousands of dollars’ worth of political ads have flooded the north Fort Bend County district in an effort to prop up Democrat Elizabeth “Eliz” Markowitz, an educator, in the longtime Republican district for the Texas House. Gary Gates, a Republican and founder of a property management company, is fighting back against the onslaught with the backing of Gov. Greg Abbott and other high-ranking Republicans along with $1.5 million of his own money added to his campaign.

The attention on the otherwise small legislative race has led to high turnout ahead of Tuesday’s special election. Nearly 18,000 voters cast ballots early and by mail during the four-day early voting period last week. The turnout eclipses the number of people who voted early over a 12-day stretch last fall when voters whittled down the original field from seven candidates to two in November.

At stake is a national effort to flip the Republican-led Texas House to Democratic control, shifting key political power ahead of the 2021 legislative session when lawmakers will redraw congressional and state legislative districts that could reshape politics for the state and nation for the next decade.

If Democrats pull off a victory, it would signal to donors across the country that they could win the nine seats needed to take control of the Texas House, said Mark Jones, a political science professor at Rice University. That could open the spigot of political donations in dozens of targeted races, including 11 in the Houston area and others in north and central Texas.

“They really have set it up as a test case of, ‘Do Democrats have a chance of flipping the Texas House in 2020?’” Jones said.

Voter registration is up across Texas, especially in Fort Bend County where 452,000 people are registered to vote, a 30 percent increase since 2014. That is faster than the population growth, which ballooned by 24 percent during the same time period.

For subscribers: Texas tops 16 million voters as registration deadline looms

Texas is politically in play in a way it has not been in years. Although Republicans control all statewide elected positions and both seats in the U.S. Senate, voter support for the GOP slipped in 2018. Democrats flipped a dozen Republican state House districts that year, and Democrat Beto O’Rourke won over a slew of counties that long favored Republicans in his failed bid for U.S. Senate.

Republicans have won House District 28 handily in past elections, including 2018 when former Richmond Rep. John Zerwas defeated Democrat Meghan Scoggins by about 8 percentage points. He retired last fall, leaving the seat vacant.

Despite Zerwas’ final electoral win, Democrats suggest Republicans are losing their grip in the district. O’Rourke lost by 3 percentage points there to Republican Sen. Ted Cruz, closing a 10 percentage-point gap from the 2016 election when then-candidate Donald Trump carried the district over Democrat Hillary Clinton.

Democrat Markowitz earned her seat in the runoff with 39 percent of the vote, followed by Gates at 28 percent, prompting a runoff. Collectively, the six Republican candidates made up 61 percent of the vote.

Regardless of the outcome of Tuesday’s election, the seat is up for election again in November.

The surge in early voting comes after months of political celebrities dropping in Fort Bend to campaign and block walk for Markowitz, including Democratic presidential hopefuls Michael Bloomberg, Julián Castro and O’Rourke. Joe Biden and Elizabeth Warren also have endorsed Markowitz.

A teacher trainer, Markowitz has reported a significant fundraising haul, in part due to the outsize attention from the presidential candidates. She has raised about $583,000 throughout her campaign, with a large chunk coming from outside Texas; she received an additional $144,000 worth of in-kind support from organizations that have provided campaign staff and other services.

Those totals do not account for the scores of out-of-state Democratic groups that have contributed or spent hundreds of thousands of dollars to aid Markowitz’s campaign, including two groups that have invested six figures each.

“People are paying attention to Texas. This is the biggest battleground state in the country. There are 38 electoral votes on the table. The state Legislature is in play for the first time since 2001,” said Odus Evbagharu, campaign manager for Markowitz. “For a long time, we’ve said Texas is on the cusp. People are starting to believe it, and you’re seeing it right now reflected in House District 28.”

The Democratic Legislative Campaign Committee, which supports Democratic candidates nationwide, spent nearly $200,000 on campaign ads supporting Markowitz, while a super PAC called Forward Majority put $200,000 into polling, direct mail and TV ads, including one earlier this month re-upping 20-year-old allegations Gates abused his children. Gates, who adopted 11 children, was accused of child abuse after punishing one of the children by sending him to school with a bag of fig bar wrappers pinned to his shirt. Although his children were taken away for several days amid further allegations of unconventional punishments, the case eventually was dropped. The Texas Democratic Party seized on the episode this month, calling on Abbott to rescind his endorsement of Gates.

On HoustonChronicle.com: Democrats attack Fort Bend state House candidate over 2000 child abuse case

Gates, who has self-funded much of his campaign, is endorsed by the governor and Lt. Gov. Dan Patrick, who argue the extensive attention on the Texas race by outside influences reflects an effort by Democrats to bring socialism to the Legislature.

“This is an important special election for a House Seat the Republicans need to hold,” Patrick said in a statement Friday. “Gary Gates will be a strong conservative voice for that district and I ask all Republicans in House District 28 to get out and vote. Don’t let Beto and the socialist Democrats steal this seat.

Republicans have responded with other attacks, including a digital ad run by Abbott’s political action committee that links Markowitz to O’Rourke and his support for a mandatory assault weapon buyback program. The Gates campaign’s tracking polls indicate the gun buyback issue has been particularly effective in mobilizing voters, said Craig Murphy, Gates’ political consultant.

Abbott also has marshaled campaign workers to canvass the district for Gates, and Republicans are busing in block walkers from around the state, according to Quorum Report, a Texas political newsletter.

Democrats have cast the voter enthusiasm as proof the traditionally red-leaning district is in play. They argue the involvement of Abbott and U.S. Sen. John Cornyn, both of whom have endorsed Gates, signals GOP concern about holding the seat.

Murphy, Gates’ political consultant, said a breakdown of early voters’ primary voting history indicates far more Republicans than Democrats have turned out so far.

“It’s super, super clear what’s happening in this election,” Murphy said. “Their path to victory seems nonexistent here. Gary Gates is winning just about every category there is except Democrats — independents, Republicans, women, various age groups. So I can’t help but be confident.”

Rebecca Deen, chair of the department of political science at the University of Texas at Arlington, is skeptical Democrats will win enough seats to take control of the Texas House.

“This might be the year,” she said. “It’s hard to tell when the year will be. All things being equal and all turnout being the turnout of previous turnout, Texas is not as purple as Democrats hope it is.”

jasper.scherer@chron.com

andrea.zelinski@chron.com