The escalating feud between Donald Trump and Ted Cruz has expanded into a fight for the backing of the GOP’s anti-establishment establishment, with both seeking validation from figures with immense influence on the right.

Trump unfurled a highly anticipated endorsement from former Republican vice-presidential nominee Sarah Palin while campaigning in Iowa on Tuesday, giving him a jolt among the party’s restless base. Palin’s endorsement came a day after Trump received the effusive praise of evangelical leader Jerry Falwell Jr., whose views could help Trump among religious voters.

But other conservative voices, many of whom had cheered Trump in recent months, have rallied to Cruz’s side. On talk radio, Mark Levin and Glenn Beck have fumed over Trump’s recent questions about Cruz’s Canadian birth. In Cruz, they see a movement leader who champions their values, whereas they say Trump is an interloper who lacks an ideological core.

The frenzied courting of conservatives is testament to their power in shaping a contest that is being dominated by two Washington outsiders. Neither has won the backing of a single governor or senator — and it’s unclear that either man even wants to. In this race, it is the media titans, personalities and activists who have long stood on the GOP’s fringe who now have all the cachet.

“You need a scorecard to keep track,” said Craig Shirley, a conservative historian. “Talk radio and bloggers — anyone outside of the system is at the center of the party, and we’re witnessing in real time the shift away from the Republican establishment in deciding who the nominee will be.”

Former Republican vice presidential candidate Sarah Palin endorsed Republican presidential candidate Donald Trump during a campaign rally in Ames, Iowa. (Reuters)

Palin on Tuesday described Trump as someone who could change the status quo in American politics, and she praised his values as a father and community leader.

“He builds big things, things that touch the sky,” she said as Trump looked on, glowingly. “He has spent his life looking up.”

Of the GOP leadership and critics of Trump, she said: “They are so busted. . . . What the heck would the establishment know about conservatism?”

After Palin finished, Trump waved and put his arm around her. “We’re going to give them hell,” he said as the crowd roared.

The value of Palin’s endorsement was hotly debated Tuesday, with Trump supporters saying her popularity in Iowa will give the reality-TV star a significant lift and Cruz backers playing down her impact.

Barry Bennett, Ben Carson’s former campaign manager, sided with those who thought it was consequential. “I think Sarah Palin actually helps Trump a lot because she’s showing them that it’s okay,” Bennett said. “Whatever lack of credentials he has, he’s making some inroads into places where we didn’t think he’d play.”

One key Cruz ally said Palin could help Trump win over women. “He’s a thrice-married, non-churchgoing billionaire, and she gives him credibility with conservative women,” said Kellyanne Conway, who manages a Cruz super PAC. “It’s a net positive.”

Ted Cruz said on the campaign trail on Jan. 19 that "Sarah Palin is fantastic," despite her endorsement on Republican presidential front-runner Donald Trump. (Dalton Bennett/The Washington Post)

Palin’s move came as a surprise to some in her orbit, given her friendly rapport with both Trump and Cruz. In 2011, she dined with Trump at a pizza shop in New York as she mulled her own White House bid, and, according to Republicans familiar with her thinking, she has been increasingly enthusiastic about Trump as he has surged in the current race. Their circles also overlap: Trump’s political director, Michael Glassner, is a former Palin aide.

Aside from Palin, Trump’s campaign is backed by prominent conservatives such as activist Phyllis Schlafly and radio host Michael Savage. Willie Robertson, a star of the “Duck Dynasty” ­reality-TV show, is with Trump, too.

Last week, it was Cruz who won the support of another “Duck Dynasty” star, when Phil Robertson signed on. The senator from Texas is also backed by longtime activists such as L. Brent Bozell III and Richard Viguerie, social conservative leader James Dobson, and actor James Woods.

It is on talk radio, especially, where Cruz has built support, which has proved critical now that Trump has taken to attacking him relentlessly. Most of these drive-time and lunch-hour heroes to rank-and-file Republicans were initially complimentary of Trump’s focus on illegal immigration last year, but they have since soured.

“I’m sick and tired of stupid talk!” Levin said Monday on his program. “This is why I’m sick and tired of stupid issues! I didn’t spend 40 years of my life — 45 to be exact — to reach a point where we actually might take back the White House with somebody who is conservative, whomever that is, to be discussing birther issues!”

On Saturday, Beck will appear in Waterloo, Iowa, at a rally hosted by a pro-Cruz super PAC. Those who are planning to be with Beck onstage attest to Cruz’s strength on the right in the state: Rep. Steve King, conservative author David Barton and Christian organizer Bob Vander Plaats. Cruz is banking on that deep goodwill, carefully built up over the course of the 2013 government shutdown and the 2014 elections, to sustain him.

Trump and Cruz had spent most of the campaign praising each other, but they have switched to attack mode ahead of the Iowa caucuses on Feb. 1.

Trump’s case against Cruz is more temperamental than ideological. He has called the Texan “nasty” and disliked by his Senate colleagues, and has wondered aloud, repeatedly, whether Cruz’s birth in Canada leaves him vulnerable to lawsuits over his citizenship.

“When you talk about temperament, Ted has got a rough temperament,” Trump said Tuesday in Winterset, Iowa, ahead of the Palin event. “You can’t call people liars on the Senate floor, when they are your leader.”

Cruz has a more understated approach. He mostly avoids taking personal shots at Trump and keeps his emphasis on the policy differences between them, pointing out where the businessman has sided with Democrats, in particular.

“If you’re looking for someone who’s a dealmaker, who will capitulate even more to the Democrats and give in to Chuck Schumer and Harry Reid and Nancy Pelosi, then perhaps Donald Trump is your man,” Cruz told reporters Tuesday at a stop in Barnstead, N.H.

Palin’s endorsement, which came after days of teasing by Trump’s campaign and widespread speculation on cable TV, riled the right in the hours before it was made official.

Appearing Tuesday morning on CNN, Cruz spokesman Rick Tyler called Palin’s expected nod a “blow” to her reputation because “she would be endorsing someone who’s held progressive views all their life.”

“I think if it was Sarah Palin — let me just say, I’d be deeply disappointed,” he said.

Supporters of Palin and Trump responded with fury. In a blog post, Palin’s eldest daughter, Bristol, wrote that Tyler’s remark “makes me hope my mom does endorse Trump.”

By the afternoon, after Sarah Palin’s endorsement, Cruz felt compelled to clarify that Tyler’s view did not reflect his own. “I love Sarah Palin. Sarah Palin is fantastic,” he told reporters. “I will always remain a big, big fan of Sarah Palin’s.”

The drama Tuesday was not limited to the right. Fault lines were beginning to be drawn by members of the GOP leadership as they grappled with the possibility of having the race come down to Trump or Cruz, rather than a candidate who is a more natural fit with donors and party brass.

Speaking at an Iowa energy summit, Gov. Terry Branstad (R) called Cruz an “opponent of renewable fuels” who should be defeated.

Trump reacted gleefully on Twitter: “Wow, the highly respected Governor of Iowa just stated that ‘Ted Cruz must be defeated.’ Big shocker! People do not like Ted.”

Branstad’s position reflects a broader unease with Cruz among Republican leaders. In Trump, most party leaders see a candidate who is unpredictable and controversial, but far less ideological than Cruz and, therefore, more likely to work with them. Several have reached out to Trump in recent weeks as their preferred candidates have stalled in the polls.

Cruz was dismissive of Branstad and said the development signals his own stature as the race’s only true conservative outsider. “It is no surprise that the establishment is in full panic mode,” Cruz told reporters Tuesday.

Rush Limbaugh, who has not picked a side in the Trump-Cruz standoff, said on his program Tuesday that “Trump is trying to position Cruz as angry, unstable, can’t get along with anybody, and thus will not be able to do deals. . . . Cruz is trying to highlight Trump’s past liberalism, ‘New York values,’ what have you. . . . Now, we’ll see if this works.”

Jenna Johnson and Jose DelReal in Iowa, and Philip Rucker, David Weigel and Katie Zezima in New Hampshire contributed to this report.