TARRANT COUNTY, Tex. — The middle-class suburbs of Fort Worth have been a stronghold for statehouse Republicans for decades. But candidate Joe Drago says he and the other Democratic challengers in this rapidly growing county will break that streak this year.

"We are seeing working-class people moving out of urban areas and into the suburbs, and that has changed the demographics profoundly," he said. "We believe a lot of these people are Democrats."

Sprawling housing developments filled with young, diverse families have crowded out the cattle farms and open fields in Drago’s district, convincing Democratic leaders that they have a chance to flip his and 21 similar state legislative districts this November. Democrats need nine to take control of the Texas House for the first time since 2003.

The party plans to funnel tens of millions of dollars into the effort, an unprecedented push that could become one of the most consequential political battles of the year. If Democrats are successful, it would raise questions about Texas’s future as a Republican bulwark in national politics.

“Republicans really haven’t come to grips with an understanding of what is happening in Texas,” said Manny Garcia, executive director of the Texas Democratic Party. “You have a rising, new Texas electorate.”

Minorities now make up more than half of the population in once solidly Republican Tarrant County, where Drago’s district is located. Wavering support for President Trump in the suburbs has further boosted Texas Democrats’ confidence, as well as blowback to conservative GOP policies on health care and education in the state.

Backed by an infusion of cash from donors nationwide, the state party plans to capi­tal­ize on the moment using tactics and organizing efforts rarely deployed in local races, including opposition research.

But many political analysts remain skeptical of Democrats’ chances, and Texas Republicans say they are prepared to slow, if not stall, Democrats’ suburban gains, which included picking up 14 state legislative seats in 2018.

GOP strategists’ confidence was boosted in January when the party won a special election for a Texas House seat in suburban Houston. Former presidential candidate Beto O’Rourke and a host of other prominent Democrats campaigned heavily to flip the seat in Fort Bend County, but the GOP candidate won by 16 percentage points.

Republicans are hoping to mount a successful defense statewide and have reenlisted the help of political strategist Karl Rove, who helped shape the GOP’s rise to dominance in Texas decades ago. Rove is working with consumer data to identify and register new GOP voters in Texas suburbs.

“One lesson from the 2018 election is, some of our candidates had gotten a little overconfident,” said James Dickey, chairman of the Texas Republican Party. “But nobody is doing that in 2020.”

Republicans are fighting against a tide of demographic change. Since 2016, Texas has added 2 million registered voters, about half of them under age 25, and 36 percent of them Hispanic, according to Tom Bonier, executive director of TargetSmart, a Democratic data firm.

Texas Democrats say they believe there are an additional 2.3 million unregistered eligible voters, the vast majority of whom are people of color or under age 35.

In parts of Tarrant, which includes Fort Worth and its suburbs, the population changes have turned the area into a political battleground. Tarrant County was an epicenter for tea party opposition to former president Barack Obama’s policies. But Trump carried the county with just 52 percent of the vote in 2016, and O’Rourke narrowly won it in his 2018 contest against U.S. Sen. Ted Cruz (R).

Now Democrats are targeting five statehouse seats there, and Republicans consider the challenge to be a defining threat to their party’s effort to cling to power statewide.

“We are the last urban county in Texas that is red, as all the other large urban counties in Texas have already turned blue,” said Jeremy Bradford, executive director of the Tarrant County GOP. “We know we are now ground zero for these races . . . because we are kind of the last defense in keeping Texas red, and that is not something we take lightly.”

Minority voters are registering at higher rates in Tarrant County than they are in Texas and nationally. The number of Hispanic registrants there grew by 6.4 percent since November 2018, higher than the state average of 5 percent, according to a Washington Post analysis of data from L2, a nonpartisan voter data firm.

Drago’s district is centered in Mansfield, a suburb where the population has grown nearly tenfold over four decades.

In the 1960s, Mansfield was nationally known as one of the last Texas school systems to integrate as local officials defied federal court orders for years. Today, white, black and Latino children account for about 30 percent each of the student body.

Drago said the region’s increasing diversity will power his campaign as he works to drive up Democratic turnout in a district that Cruz carried by fewer than 100 votes in 2018.

Drago will be counting on voters such as Bernadette Amao, who in December bought a 4,000-square-foot house in one of Mansfield’s newly built subdivisions. She checks the mail regularly to see whether her and her husband’s voter registration cards have arrived.

“I always vote, and that will be especially true this year,” said Amao, who immigrated to Texas from Nigeria in 1997 and says Trump is too divisive. “If local Republicans continue to support President Trump blindly, I will not be voting for any of them.”

Polls show that Trump’s popularity has been declining across suburban Texas, which Democrats say helped them pick up two congressional seats in 2018.

“From mid-2016 to now, I just keeping having more and more people come up to me and say, ‘I have been voting for Republicans for years, and I just can’t do it anymore,’ ” said Matt Angle, founder of the Lone Star Project, a Democratic-aligned political action committee.

Angle is referring to voters such as Kathy Griffin, a 68-year-old Mansfield resident who has voted for Republicans in the past — including for Sen. Mitt Romney (R-Utah) during his 2012 presidential campaign. By 2018, she was so disgusted with Trump she planted a sign for O’Rourke, then the Democratic candidate for U.S. Senate, in her yard.

“I hope we run [Trump] out of town on a rail, tarred and feathered,” said Griffin, a retired schoolteacher. “He’s a liar . . . so for me, it will be Democratic up and down the ballot.”

Republican leaders say they are confident that Trump won’t be as toxic for the party in the suburbs as he was two years ago, particularly if Sen. Bernie Sanders (I-Vt.), a democratic socialist, is the Democrats’ presidential nominee.

“Now, there is a choice on the ballot, and it’s not just Trump versus nobody or just a question about whether, ‘Do you like Trump?’ ” said Chris Murphy, an Austin-based GOP strategist.

The healthy economy achieved under Republican leaders will boost their chances of maintaining control, Republicans say. Drago’s Republican opponent, Mansfield Mayor David Cook, predicts that voters — even the diverse newcomers to his district — will reward Gov. Greg Abbott and other Republicans for the state’s 3.5 percent unemployment rate, which is near a record low.

“Texas is still a Republican-leaning state,” Cook said. “And the people who are moving to Texas do so for a reason — the economy is great in the U.S., and it’s even better in Texas.”

But when it comes to other local issues, Drago and other Democratic candidates say the political dynamics are on their side, including Republicans’ refusal to expand Medicaid and increase funding for public schools.

In Mansfield, for example, parents have been complaining that school overcrowding has forced some students to be bused to other locations.

“Our state constitution charges us with providing a good, strong public education, and there is a tendency on the Republican side to not put an emphasis on public education,” Drago said.

In response to the GOP losses in 2018, Abbott and Republican lawmakers pushed through an $11.6 billion plan to boost funding for public schools.

“On public education, the state is moving in the right direction,” Cook said.

One issue in Tarrant County expected to remain especially divisive is gun control.

Last year, after a shooting at an El Paso Walmart killed 22 people, some Republicans worried their policies were at odds with suburban residents who were clamoring for more restrictions on firearms. But GOP leaders say the political consequences of the gun debate shifted in December when armed security guards at a Fort Worth church shot and killed a gunman who opened fire during Sunday services.

“You have had absolutely tragic events that have happened with guns, but there have also been equally tragic events that have been prevented by guns, too,” said Bradford, of the Tarrant County GOP.

For national Democrats, however, the party’s success last year in flipping both houses of Virginia’s legislature serves as a model for what they think is possible in Texas.

Jessica Post, executive director of the Democratic Legislative Campaign Committee (DLCC), noted that Texas and Virginia both allow unlimited campaign contributions to legislative campaigns. Those laws will enable the DLCC to partner with labor unions and other left-leaning groups to spend heavily on Texas races.

“I think we will see even larger levels of spending in Texas than we saw in Virginia,” Post said.

Still, Cal Jillson, a professor of political science at Southern Methodist University, remains skeptical that Democrats will have the resources to turn out a lot of nontraditional voters.

“The Democratic institution in Texas has been so weak for so long that even if they knew where every one of those people were, they would not be able to create the volunteer force needed to get there on the doorstep to register and turn them out,” Jillson said.

But here in Tarrant County, Democratic House candidate Lydia Bean remains convinced she can pair big money with grass-roots campaigning to help flip Tarrant County.

Bean’s mother ran for the statehouse seat two years ago and received 46 percent of the vote after spending just $30,000. Bean, who runs a nonprofit organization, plans to raise nearly 20 times that amount this year.

As she canvassed for votes near Six Flags Amusement Park, Bean walked with a digital device identifying names and addresses of potential voters. At the home of one Latino couple, Bean discovered that the wife was not registered to vote.

“What do you think about Trump?” Bean asked the couple.

“I think he is doing a good job, and the economy is good,” said Gus Medina, surprising Bean.

Despite that letdown, Bean still considered her visit to be a success.

“I think he’s persuadable, and now we know his wife is not even registered,” said Bean, who will be back at Medina’s door before November.

Lenny Bronner contributed to this report.