WASHINGTON — Texas Republicans are fretting that Sen. Ted Cruz's close call signals that their long grip on the state will end unless they can reach beyond the party's die-hard base next — and blunt Democrats' enthusiasm to oust President Donald Trump.

"I don't think we can take for granted that Texas will be reliably Republican in the foreseeable future, unless we take care of our business," said Sen. John Cornyn.

Cornyn is already girding for a fight next year, when he'll ask voters for a fourth term. That's early for an entrenched incumbent. But, he said Wednesday, Republicans have been too complacent, taking for granted that they'll sweep Texas elections as they've done since 1998.

Suburban voters abandoned the party in droves in November, when Beto O'Rourke held Cruz below 51 percent. That was the best showing for a Democrat in Texas in decades, putting a scare into Republicans and catapulting O'Rourke to the top tier of potential White House contenders.

"President Trump was responsible for 100 percent of the turnout," Cornyn said. "Fifty percent turned out because they wanted to support the president. Fifty percent turned out because they wanted to defeat him. Effectively, this was a referendum in some sense on him. That's still going to be a factor in 2020."

More than a third of the electorate will be nonwhite, the most ever, according to an analysis released Wednesday by the Pew Research Center.

Texas has been diversifying for years, and the shift tends to favor Democrats, who picked up two U.S. House seats in Texas in November, in Dallas and Houston, plus a dozen state House seats and two seats in the state Senate.

In 2016, Trump beat Hillary Clinton in Texas by just nine percentage points — far worse than GOP nominee Mitt Romney's 16-point margin over Barack Obama four years earlier.

Nonwhite voters overwhelmingly backed O'Rourke over Cruz, according to a Latino Decisions 2018 survey.

Pew estimates that Hispanics nationally will account for 13 percent of eligible voters next year, making them the biggest racial or ethnic minority in the U.S. electorate for the first time.

Turnout rates are generally low among eligible Hispanics, though, and they are not a monolithic political bloc.

"We're going to be the key swing votes in Florida, in swing states like Arizona, in Colorado," said Domingo Garcia, national president of the League of United Latin American Citizens and a former member of the Dallas City Council and the state House.

"Both parties need to be paying attention that the Latino vote is real," Garcia said. "We saw record Latino turnout in Texas, where Beto O'Rourke almost beat Ted Cruz. We saw it in Nevada, where the Latino vote was crucial in electing a Democratic senator, in Arizona, where they elected the first Democratic senator in a long time."

Texas tipping point?

In Texas, Democrats have pined for a tipping point for years.

Republicans have worried that if and when that day comes, they'll lose control of Texas — and any hope of winning the White House. Democrats hold a strong grip on California and New York, and GOP chances would plummet without Texas' 38 electoral votes.

"The challenges we face in Texas are very real," Texas GOP chairman James Dickey told the conservative Washington Examiner, which reported that he had been warning national GOP leaders and the White House that Trump could lose Texas unless he invests significant time and resources there in 2020.

Steve Munisteri, who led the state GOP from 2010 to 2015, said Dickey is right to sound the alarm that Texas can't be taken for granted.

"The Democrats are fired up because of President Trump, and therefore we can't ignore the fact they will probably have a good turnout," he said. "You should treat Texas as a swing state. ... It's not as red as people think it is. It's actually a competitive state, it's just that we keep winning."

Munisteri has worked at the White House the last two years as a liaison to business, a post he’ll leave on Feb. 8 to join the Cornyn campaign as a senior adviser. Cornyn announced the hiring Wednesday.

He’s also hired John Jackson, who ran Gov. Greg Abbott’s re-election effort, as campaign manager.

No major Democratic contenders have yet emerged for the Cornyn seat. With endorsements from Lt. Gov. Dan Patrick and other key conservatives, Cornyn isn’t expected to face a serious challenge in the primary. If O’Rourke or Julián Castro, the former San Antonio mayor and Obama housing secretary, were to end up on the Democratic ticket, that would add more excitement for Texas Democrats.

Cornyn endorsed Cruz, and he returned the favor. But Cruz is far more pugilistic and divisive. Cornyn projects a more measured demeanor, and just ended a stint as majority whip, the GOP's No. 2 leadership post in the Senate.

That, said Munisteri, makes Cornyn “exceptionally well-positioned” not to push away independent voters. “Cornyn can extend his reach beyond the base.”

That’s not one of Cruz’s hallmarks.

Message factors

Demographic shifts played an important part in the Cruz-O’Rourke contest. But Cornyn identified other factors, too.

“We've gotten a little complacent when it comes to running races in Texas, assuming that Republicans would always win the general election and focusing almost exclusively on the primary in terms of who we think we're talking to and the kinds of messages that we deliver,” Cornyn said.

“All of those birds came home to roost in 2018 — sort of a perfect storm. You had a very popular Democratic nominee” — O’Rourke, who managed to raise $80 million that he used to deploy 800 election workers in an unusually effective get-out-the-vote operation.

Cornyn noted that turnout in last year’s midterms, 8.3 million, was a huge jump from the 4.7 million Texans who voted in 2014, when he was last on the ballot.

“Obviously we lost a number of the suburbs," he said. "And I think in part that's because of the fact we were hung up on the primary message, rather than talking about things like education and health care and traffic — things that really, I think, more likely appeal to a suburban audience.”

“What Beto O’Rourke demonstrated is not only do you have to be concerned about the primary, you have to be concerned about a general election. And those are different electorates,” Cornyn said. “Those are much larger audiences, and you need to have a message that's appropriate to that larger general election audience."