Sen. Ted Cruz during a lunch with colleagues last week in Washington passed the hat for campaign cash, as the Texas Republican’s anxiety mounts about the unusually brisk challenge from Democratic Rep. Beto O’Rourke.

O’Rourke is raising money by the truckload — enough to compete in Texas, a big state with costly media markets. The development has forced Cruz to hunt for resources in unlikely places for a politician who built his national career on opposition to the party establishment: fellow lawmakers, political action committees, and wealthy Republican donors.

“He was pretty intense last week and he should be — he needs the dough,” said a GOP operative, requesting anonymity in order to speak candidly about Cruz’s pleas for contributions from Republican senators and their political action committees.

O’Rourke, 45, a third-term congressman, has caught the imagination of liberals across the country. They’ve poured cash into his campaign, primarily in small donations, despite the long odds of prevailing in Texas, a state that hasn’t elected a Democrat to statewide office in several years.

[Poll: Ted Cruz in dead heat with Beto O'Rourke]

From Jan. 1, 2017, through June 30 of this year, O’Rourke raised nearly $24 million. He more than doubled Cruz’ fundraising during the first six months of this year, and as of July 1 had more than $14 million in cash on hand to spend against Cruz. Comparatively, the senator banked only $9 million.

O’Rourke’s financial advantage appears to be the primary issue rattling team Cruz. It’s raised more alarm bells than public opinion polls showing a close race in the midterm election, with the incumbent leading by an average of 5.5 percentage points.

Indeed, Cruz’ big obstacle in the money chase is convincing Texas’ vast community of wealthy Republican donors that he needs help (the senator waltzed to victory in his general election six years ago.) They could give, or direct, tens of millions to the senator’s campaign and affiliated super PAC, “Texans Are.” But many are more worried about vulnerable GOP House members in suburban Austin, Dallas, and Houston, as well as a slew of endangered state legislative seats.

“It’s just not on my radar screen,” John Nau, a major Republican donor in Houston who has been active in past Senate races and raised money for Senate Majority Whip John Cornyn, R-Texas, told the Washington Examiner. “I don’t have an opinion on the U.S. Senate race one way or the other… Ted’s going to win.”

That’s not Cruz’s only problem with Texas’ big donors.

Cruz spent the first four years of his Senate tenure trashing the establishment wing of the Republican Party that contributors and bundlers affiliate with. He initiated a government shutdown that was doomed to fail and meddled in the House to torpedo GOP leadership strategy for countering then-President Barack Obama.

Cruz has toned down his fiery rhetoric and provocative antics since losing his bid for the Republican presidential nomination in 2016. He’s worked to build bridges to Senate Republican leadership and other establishment figures, with some party insiders complimenting him for constructive efforts to build consensus.

But GOP donors in Texas have been slow to forgive, with Cruz’s support for anti-establishment Republicans in down-ticket primaries contributing to their lingering suspicion.

“The bulk of these donors can’t stand Cruz,” said a connected Republican operative in Texas, on condition of anonymity.

Cruz emerged from his presidential run bruised.

The Republican base in Texas resented him for refusing to endorse President Trump at the GOP convention in Cleveland. Suburban Texans who traditionally vote Republican but are drifting from the party because of dissatisfaction with Trump continued to keep the senator at arms-length, repelled by his similar brand of culture war politics.

Cruz has resuscitated his image in the nearly two years since. Republican insiders close to the senator say his political standing is higher than recent public polls suggest. These surveys have sampled registered voters, even though voter turnout in Texas has consistently proven that polling “likely voters” produces more accurate data. Meanwhile, Republicans argue, not without some merit, that O’Rourke is too liberal for Texas.

But Republicans are treating the race as though it’s competitive, conceding that Cruz could lose. Most worrisome is the combination of a rough midterm environment for Republicans; Cruz’s favorable ratings, which are treading water; and the turn against Republicans in Texas’ affluent, major metropolitan suburbs, especially among women, which account for a big chunk of the electorate.

“I’m freaking worried,” a Republican consultant monitoring the campaign said. “Cruz is going to have to unleash very serious negatives on Beto. He needs to turn this into a race that’s all about Beto’s record and Beto’s views."