Fort Worth billionaires Robert and Anne Bass — frequent liberal donors in the heart of one of the country’s largest, urban conservative strongholds — are among the top contributors to national Democrats’ efforts to flip the Senate this fall.

Whether any of that money makes it back to Texas, where Democrat Beto O’Rourke is waging a spirited campaign against Republican Sen. Ted Cruz, remains uncertain.

O’Rourke has asked political action committees to stay out of his race, and national Democrats see other races as more winnable.

Yet Texas is a major source of donor money for both political parties, and likely to feature one of the most high-profile Senate races on the map this fall.

“Most donors don’t just want to be an ATM,” said Dallas attorney Marc Stanley, a major national Democratic donor who is raising money for an anti-Cruz super PAC.

“In the past our Senate races haven’t been close enough to get attention from [Democrats’ Senate campaign arm],” he added. “I would imagine this time… donors are making their case for the money to be spent locally.”

Democrats are defending 24 Senate seats this cycle, including 10 incumbents in states President Donald Trump won.

Republicans hold 51 of the Senate’s 100 seats, and must defend two seats without incumbents seeking re-election, Arizona and Tennessee, as well as one state, Nevada, where Democrat Hillary Clinton won.

“We are still in an environment where major Texas Democratic donors give to out-of-state organizations who will spend the money other places,” said Texas Democratic strategist Matt Angle, who twice ran Democrats’ House campaign arm in Washington.

“Many of these donors know the money is not coming back to Texas, but they give because of their concern about holding Democratic seats in the U.S. Senate,” said Angle.

Anne and Robert Bass could not be reached for comment. They’ve each given directly to Democrats elsewhere in the country this election cycle. Robert Bass gave the maximum contribution to Georgia’s Jon Ossoff last year,the Democrats’ House candidate in the first special election after President Donald Trump was elected.

The couple also gave checks for $2,700 — the maximum donors can give a single candidate — to O’Rourke’s campaign after the March Texas primary.

Super PACs can receive unlimited contributions, but can’t coordinate directly with candidates.

The main super PAC supporting Senate Democrats, Senate Majority PAC, has raised $70 million, according to the most recent fundraising report, which ran through June 30.

Senate Majority PAC received $400,000 from Anne Bass, and $350,000 from Robert Bass, who Forbes estimates is worth $4.9 billion. Robert Bass and his siblings, some of whom help Republican candidates, inherited a family oil fortune.

Senate Majority PAC also received another $100,000 from Flower Mound attorney Thomas Black. All three Texans are among the group’s top donors.

Chris Hayden, a spokesman for Senate Majority PAC, declined to comment on the group’s plans for Texas or specific donors. An aide for the Democrats’ Senate Campaign Committee said the group is “monitoring the race” in Texas.

“Texas Democrats must save ourselves,” said Angle, who founded a political action committee, Lone Star Project, aimed at raising money primarily for state and local Texas candidates.

O’Rourke said roughly 70 percent of his campaign contributions so far have come from Texas. He more than doubled Cruz’s haul in the most recent reporting quarter, with an average donation size of $33, according to his campaign.

GOP leaders in Washington aren’t eager to send Texans’ money back this cycle to help Cruz. Texas Sen. John Cornyn, No. 2 in the Senate Republican leadership, is raising money to give away to candidates in other states.

If needed however, Cruz’s national super PAC allies have said they’ll come to his defense this fall.

The House landscape in Texas is a different story.

Democrats need to pick up 23 seats to win a House majority this fall, and are targeting five GOP-held seats in Texas. Clinton carried three of those districts, in San Antonio, Dallas and Houston.

Fort Worth’s main congressional district, held by long-time GOP Rep. Kay Granger, is nowhere on national Democrats’ target map. Trump carried it with 63 percent of the vote.

This week Anne and Robert Bass each wrote checks for the maximum amount to Granger’s Democratic challenger,Vanessa Adia, who has been campaigning hard across the district. Granger, on the other hand, has not publicized any campaign events for her re-election.

Anne and Robert Bass have also given a combined $43,000 to Democrats’ House campaign committee. Anne Bass gave $150,000 to a super PAC aligned with EMILY’S List, which supports women candidates who support abortion rights running for office at all levels.