AUSTIN, Texas (Reuters) - A jump in turnout for Democrats in the Texas primary election on Tuesday strengthened forecasts that anger over U.S. President Donald Trump’s policies could help the party flip congressional seats from Republican control in November.

But in the first U.S. primary of the 2018 midterm election season, Republicans also flexed their muscles. Early returns showed the party that has dominated Texas politics for decades was on track to be well ahead of Democrats in overall primary voters statewide.

Democrats need to gain 24 seats nationwide to retake the U.S. House of Representatives, a feat that would allow the party to block the Republican president’s legislative agenda.

“This isn’t about Democrats turning Texas blue or even purple,” said Mark Jones, a political science professor at Rice University in Houston.

“The enthusiasm advantage that Democrats have in 2018 compared to 2014 should help them pick off a few toss-up U.S. Houses seats held by Republicans,” he said.

Texas Democrats were fielding their largest contingent of congressional and legislative candidates in a primary in several decades. They were encouraged that a turnout set to be nearly double of what it was in 2014 was a sign of electoral success to come in the most populous Republican-held state.

Texas Democrats, however, have not won a statewide race for posts such as governor or U.S. senator in more than two decades.

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For the first time in more than 25 years, Democrats were contesting each of Texas’ 36 U.S. congressional districts, the party said.

Texas Democrats see the party’s best opportunities in the six Republican-held districts where incumbents are not seeking re-election. They also are targeting at least two Republican incumbents whose support bases have weakened, in part due to shifting demographics.

Even though Trump was not on the ballot, his presence was felt in the primary vote. His policies pushed to the polls Democrats who oppose him and Republicans who support him, analysts said.

Early voting for Texas Democrats hit a record for a midterm election in the state’s 15 most populous counties and was double the figure posted in 2014, the Secretary of State’s office said.

Trump has been divisive in Texas, where he receives about 83 percent approval among Republican respondents and 85 percent disapproval among Democrat respondents, according to polling from the Texas Politics Project at the University of Texas.

Some of the issues that helped Trump nationally, such as reworking trade deals like the North American Free Trade Agreement (NAFTA), can be vulnerabilities in Texas, where the state’s economy is heavily dependent on trade with neighbor Mexico. His plans to crack down on immigrants have spurred political activism among Latinos, who make up about 40 percent of the state’s population and tend to support Democrats.

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Runoff elections are expected on May 22 in some of the most heavily contested districts where one candidate is unlikely to receive the majority required to win outright. In central Texas’ 21st Congressional District, for example, run-offs are on tap for both parties after 18 Republicans and four Democrats ran for the seat vacated by Republican Representative Lamar Smith.

Republicans Senator Ted Cruz and Governor Greg Abbott, who easily won their primaries, used the Democratic surge in early voting to appeal to the party faithful to go out to the polls.

Abbott already has a war chest of about $41 million, more than the combined funds at this point of every Democratic candidate running in the state for governor, lieutenant governor and the U.S. Congress.

The best-funded Democratic candidate is Beto O’Rourke, a U.S. House member running for the U.S. Senate with calls for universal healthcare, new restrictions on gun ownership and immigration reform. He has been projected to win his primary race but is considered a long-shot to beat Cruz in November.

With about 70 percent of the precincts reporting, O’Rourke received about 505,000 votes in the Democratic primary and Cruz had about 1.1 million in the Republican race.

“If Democrats are able to pick up one or two U.S. House seats previously held by Republicans and cut into Republican margins in the state legislature ... that would show that the party’s ‘blue wave’ is no mirage,” said Cal Jillson, a political analyst at Southern Methodist University in Dallas.