Voters in the fast-growing Houston suburbs will offer a rare glimpse into a critical segment of the electorate on Tuesday when they elect a new state representative, in what could prove an early bellwether ahead of the 2020 presidential elections.

But the race to fill a seat that became vacant when the Republican incumbent, state Rep. John Zerwas, left to take a university job has become a magnet for outside Democratic groups who hope to send a message that Texas and its treasure trove of electoral votes are in play.

Democratic groups have invested more than $600,000 in Eliz Markowitz, an education specialist making her second run for public office this year. Markowitz scored 39 percent of the vote in a November all-party primary to secure a spot in the runoff.

Republicans split the remaining 61 percent of the vote in that November primary, tempering Democratic hopes for a big win.

“There's a substantial gap between Republican votes and Democratic votes. It is only a competitive race because the energy is on the Dem side. It's still a very tough race,” said Mustafa Tameez, a veteran Houston Democratic strategist. “There’s a lot of energy on the Democratic side, and people can smell victory. So they’re coming to the table and investing more.”

But state Republican observers say the candidate who will represent them on the ballot Tuesday, perennial candidate Gary Gates, could make the race competitive. One of the Democratic groups backing Markowitz, Forward Majority, has aired television advertisements highlighting a 2000 court case against Gates that alleged he abused adopted children.

Gates took 28 percent of the vote to win the second slot in the runoff, and he has spent $1.5 million of his own money on the race, public campaign finance disclosures show.

“Gates is a perennial candidate with personal wealth and baggage. Even if he wins, his hopes to be the Republican nominee in 2020 are in doubt,” said Corbin Casteel, a longtime Texas Republican strategist.

The district, based in Fort Bend County, is a microcosm of a peculiar moment in Texas politics.

Once House Majority Leader Tom DeLay’s power base, Fort Bend has added more than 200,000 new residents since the 2010 census, making it the 10th-fastest growing county in America in the past decade.

It is increasingly diverse, thanks to influxes of African American and Asian American residents who each make up about a fifth of the local population. About a quarter are Hispanic, and about a third are non-Hispanic whites.

The ultimate winner might not ever get to cast an actual vote in the state legislature, which only meets in odd-numbered years. Markowitz or Gates would have to run again in the March 3 primary and in November’s general election, and reelection is not guaranteed in what will certainly be a much broader electorate.

But the race is a symbolic test of Democratic strength in the suburbs, a key battleground especially in Texas. Texas Democrats won U.S. House seats in suburban Houston and Dallas in 2018, and state House candidates made significant inroads in overlapping districts, picking up 12 seats in the 150-member body.

Democrats need to pick up a net of nine seats to win control of the Texas state House, a chamber they have not controlled in more than 20 years. If the party manages to win those seats, Democrats will earn a place at the table when state legislators redraw political boundaries after the 2020 census.

“Texas obviously is sort of the crown jewel of redistricting,” said Jessica Post, who heads the Democratic Legislative Campaign Committee, which has given Markowitz’s campaign almost $200,000.

On the GOP side, Gov. Greg Abbott (R) has dispatched an army of volunteers to knock on doors for Gates.

“A Democrat win would be a symbolic victory in an historically Republican suburban county that is trending purple, if not blue. A Republican win would be a maintenance victory, holding a reliable seat,” Casteel said. “Special elections historically stand alone. But the victor is wise to message otherwise to their base of support.”