For the first time in decades, Democrats are making a big play for Texas in 2018.

There are Democratic candidates running in all of the state’s 36 congressional districts for the first time in 25 years. Democrats know they won’t be competitive in every congressional district, but they have their sights set on the three they believe they have the best shot at winning — the Seventh Congressional District in Houston against incumbent Rep. John Culberson, the 23rd Congressional District outside San Antonio against incumbent Rep. Will Hurd, and the 32nd Congressional District in Dallas against incumbent Rep. Pete Sessions.

There were signs before 2018 that these three districts could be shifting blue; namely, the fact that Hillary Clinton carried all three by a couple of points in the 2016 election.

A popular Democratic Congress member, Rep. Beto O’Rourke, is challenging (and out-fundraising) Sen. Ted Cruz in the race for US Senate. O’Rourke is criss-crossing the state talking about progressive values and energizing the state’s base in the process. And though Democrats are facing tremendously steep odds in the governor’s race against incumbent Greg Abbott, they are still trying, with two strong candidates in Tuesday’s runoff.

Democrats are also fielding competitive candidates in three more Texas congressional districts they see as more of a long shot but still in play: the Second, 21st, and 31st.

“We’re definitely seeing unbridled enthusiasm among Democrats,” said Mark Jones, a political science professor at Rice University in Houston.

To be sure, competing seriously in Texas is still a long shot for Democrats. Sessions and Culberson, in particular, are formidable incumbents who have been in office since the early 2000s. But the fact that there were fields of seven Democratic candidates lining up to challenge each one in March is notable in a state where those primary fields were empty just two years ago.

In 2016, “They couldn’t even find a gadfly to run,” Jones said. Now, “Not only are you seeing a large number of Democrats file [paperwork to run], but you’re seeing some really top-tier candidates. Democrats came out of the woodwork.”

Those huge fields of Democratic candidates were winnowed down to two in the first round voting in the March primaries. On Tuesday, Democrats will select their nominees in each race.

Democrats got a taste of good news in 2016 with Clinton’s better-than-expected margins in these congressional districts. Fast-forward a year and a half; now Democrats have already pulled off a long-shot win in deep-red Alabama in 2017.

They could repeat that in Texas if they can do two things at once: spur Hispanic and Latino voters to turn out in droves, and peel off white, moderate suburbanites who don’t like Donald Trump (particularly women).

To see whether Democrats can flip seats in Texas, these three congressional races are the ones to watch.

Why Texas could be in play for Democrats

In past years, the 23rd Congressional District was known as the only one that Democrats could plausibly win. Their map is expanding in 2018 for two big reasons: a national anti-Trump backlash and rapidly changing voter demographics in the state.

The president’s approval rating in the Lone Star State is noticeably low — 39 percent, as opposed to the 54 percent of Texans who say they don’t like him. This may seem surprising at first blush, given that Texas is thought of as the home of conservative politics. But Texas has a lot of college-educated, affluent, suburban voters, who historically don’t like Trump that much — especially suburban white women.

I've spent my career downplaying Dems' odds in Texas, but there's something different going on there this cycle. pic.twitter.com/hVvukXDjWK — Dave Wasserman (@Redistrict) February 26, 2018

It shouldn’t actually be that surprising that the state is warming to Democrats, according to Dave Wasserman, an elections analyst and the US House editor of the Cook Political Report. There are a number of reasons behind that, chief among them that Texas’s demographics are changing rapidly. The 2010 census showed about 51 percent of the state’s overall population is Hispanic or Latino. An influx of 2.7 million new Texans has come into the state since 2010; more than half are Latino.

“Democrats are doing much better anywhere there’s diversity. Texas is the ultimate multicultural state, maybe second only to California,” Wasserman said.

And it’s not just about Democrats making a play for Latino voters. There’s a large number of suburban voters, particularly women, who are dissatisfied with Trump. They could be up for grabs, and Democrats are certainly making a serious attempt.

Democrats have the demographics — but do they have the votes?

The ultimate test for Texas Democrats in 2018 will be turnout. Republicans have a firm grip on state politics. Through a mix of voter suppression, gerrymandering, and noncompetitive races they’ve been able to keep turnout relatively low in the state for years.

Even as hype about a blue wave started earlier this year, the March primaries showed that Democrats in Texas still have a lot of work to do to make the wave a reality. About 1.5 million Republicans voted in the March primary, compared to 1 million Democrats. In other words, Democratic turnout was good, but not great, and Republicans held a 500,000-vote advantage when all was said and done. Still, primary turnout doesn’t always tell us much about what will happen in November.

“Democrats like to say Texas is not a red state, it’s a nonvoting state. Fine. But the fact that it’s a nonvoting state means that it’s a red state,” said Evan Smith, CEO of the Texas Tribune and longtime Texas politics observer, in an post-election interview with my colleague Dylan Scott.

For example, non-Hispanic whites in Texas make up less of the total population but more of the active voter population. According to the US Census Bureau’s Current Population Survey, non-Hispanic whites made up 47 percent of all Texas adults in 2016 but also made up 61 percent of Texas voters that year.

A recent analysis by the Texas Tribune found part of that is due to age: A third of Texas’s Hispanic population isn’t old enough to vote yet. On the flip side, residents between the ages of 45 and 64 account for the largest age group of white Texans (and are ones who vote more).

And Texas Republican gerrymandering could come back to bite them in 2018. That’s because hyper-blue Travis County (home to Austin) was cut into five different congressional districts when Republicans redistricted. If Austin voters turn out heavily in their respective districts, it could help shift things toward the Democrats, especially in the 21st Congressional District.

“Partisan mapmakers tend to overreach,” Wasserman said. “Just because the plan has worked well until now doesn’t mean it will work well in 2018.”

No matter the outcome, 2018 results will reveal whether Democrats can turn Texas into a new electoral opportunity in future elections. As Wasserman pointed out, Texas is part of a Southern bloc of states known as the Sunbelt, along with others like Arizona, Georgia, and North Carolina, plus Southern California and parts of Florida. It’s a spot where Democrats are hoping to solidify their political future.

“That Democrats’ future is in the Sunbelt ... their Midwestern seats may not be as friendly over the long term as some emerging opportunities in the South,” Wasserman said.

Here are the key Texas primary runoffs who’s nominees will be elected on Tuesday:

Seventh Congressional District — Houston

Democrats

Lizzie Pannill Fletcher, a longtime Houston attorney

Laura Moser, a former freelance journalist and activist

Republican

Rep. John Culberson (R-TX) — incumbent

Issues

Expect disaster relief funding to become an issue as we move closer to November. Houston was hit hard by Hurricane Harvey in 2017, and many residents are still feeling the impact.

32nd Congressional District — Dallas

Democrats

Colin Allred, a civil rights attorney and former NFL player

Lillian Salerno, a former Obama administration appointee

Republicans

Rep. Pete Sessions (R-TX) — incumbent

Issues

There’s not much difference between Salerno and Allred on the issues, but Salerno has said that if Democrats retake the House, she won’t support House Minority Leader Nancy Pelosi’s bid for speaker. Allred has been more tight-lipped about how he’d vote.

23rd Congressional District — San Antonio area to the Mexico border

Democrats

Gina Ortiz Jones, a former US Air Force veteran and an official at the Office of the US Trade Representative under President Barack Obama

Rick Treviño, a San Antonio teacher

Republicans

Rep. Will Hurd (R-TX) — incumbent

Issues

Immigration is a huge issue in the massive 23rd Congressional District, which covers the vast majority of the US border with Mexico. Incumbent Rep. Will Hurd is a fairly well-liked, moderate Republican who has been trying to distinguish himself on immigration. (He was a co-author of the Hurd-Aguilar bill to protect the young unauthorized immigrants known as DREAMers.) But Democrats are likely to try to tie Hurd’s voting to Trump in the general election.

The Texas governor’s race

Democrats face very steep odds in their attempt to unseat Gov. Greg Abbott, an incumbent who is one of the most popular governors in the country.

Democrats

Andrew White, a business executive and son of former Texas Gov. Mark White

Lupe Valdez, the former Dallas County Sheriff and a US Army veteran

Republicans

Gov. Greg Abbott — incumbent

Issues

There is a slew of issues in the governor’s race, but ones sure to come up in the Democratic primary includes the state’s response to immigration and border security, infrastructure, disaster relief, education funding, and access to women’s health clinics.