In the hopes of staving off the GOP establishment’s efforts to block his nomination at a contested convention, GOP frontrunner Donald Trump hired a new delegate manager who has successfully led similar convention battles over the past several decades.

Trump has hired delegate manager Paul Manafort to lead his GOP convention efforts and shore up enough delegates to ensure he wins the nomination on the first ballot at the GOP presidential convention in Cleveland in July. Manafort is well known in GOP circles because in 1976, on behalf of then President Gerald Ford—who ascended to the presidency without being elected because of Richard Nixon’s Watergate-driven resignation—Manafort successfully fended off future president Ronald Reagan in a delegate battle that may end up looking a lot like 2016. Thanks to Manafort’s work for Ford that year, the incumbent president barely held on to the party’s nomination, beating back Reagan’s challenge.

But four years later, when Reagan faced a similar but less complicated delegate battle in 1980, he hired Manafort to lead his successful delegate fight at the convention that year.

Reagan, of course, would go on to win the nomination and then win the White House back for Republicans from the failing Carter.

Manafort also played a leading role in the 1988 GOP convention, which nominated then future President George H.W. Bush, and in the 1996 convention which nominated then Senate Majority Leader Bob Dole as the GOP presidential nominee. Dole would go on to lose the general election to incumbent Democratic President Bill Clinton.

“Yes,” Trump told the New York Times when asked to confirm the news he hired Manafort. “It is true.”

Trump’s hire of Manafort, the Times’ Maggie Haberman and Alex Burns wrote, “is a sign that Mr. Trump is intensifying his focus on delegate wrangling as his opponents mount a tenacious effort to deny him the 1,237 delegates he would need to secure the Republican nomination.”

Haberman and Burns wrote:

Under those circumstances, Mr. Trump’s opponents hope they can wrest that prize away from him in a contested convention.

Bringing Mr. Manafort on board may shore up Mr. Trump’s operation in an area where his opponents currently see him as vulnerable. In an alarming tactical setback for Mr. Trump, the Wall Street Journal reported last week that he may harvest fewer delegates from his primary win in Louisiana than Sen. Ted Cruz (R-TX) , whose campaign has aggressively picked off delegates who are uncommitted or apportioned to candidates no longer in the race. Too many missteps of that kind could force Mr. Trump unnecessarily into a Cleveland floor fight.

Similar reports in recent days have cropped up in Missouri, South Dakota, South Carolina, and many other states where Trump has dominated with the public but still infuriates party insiders. The addition of Manafort to his team decreases the likelihood that Sen. Ted Cruz (R-TX), Ohio Gov. John Kasich, any other campaign who has since suspended, or the party itself can pull off major delegate shenanigans in Cleveland.

Trump has been aiming to pivot to the general election sooner rather than later, in large part because his only two remaining competitors—Cruz and Kasich—can’t realistically beat him without a contested convention. Cruz would have to reach nearly 90 percent of the party’s remaining outstanding delegates to get there, a virtually insurmountable feat, while it’s already mathematically impossible for Kasich to get there.

Anti-Trump forces inside the GOP have hung all their hopes on a contested convention, and Trump’s Manafort hire could stave off those efforts. A fierce battle lay ahead over the next several days heading into next Tuesday’s Wisconsin GOP primary where different polls show the candidates bunched up competing closely within the margin of error, some with Cruz in front and some with Trump in front. A Trump win in the Badger State would devastate the so-called “Never Trump” group, whereas a Trump loss to Cruz would embolden his critics.

Then two weeks later it is Trump’s home state of New York, where the real estate magnate is expected to dominate. After that, the rest of the eastern seaboard—Rhode Island, Connecticut, Delaware, Pennsylvania, and Maryland—votes before the end of April. In May, Indiana, Nebraska, West Virginia, Oregon, and Washington State hold nominating contests before the final votes are cast before the July convention on June 7 in California, Montana, New Jersey, New Mexico, and South Dakota.

Theoretically, Trump could wrap everything up before or on June 7—but it’s a tough road ahead. There are also hundreds of delegates who are entirely uncommitted walking into the convention whom Trump could get to vote for him—something Manafort is undoubtedly already working on achieving.

“The move [hiring Manafort] is freighted with political symbolism: After the 1980 election, Mr. Manafort was among the young-gun Reagan operatives who founded one of Washington’s best-known political consulting and lobbying shops,” Haberman and Burns wrote in the Times. “His principal business partners were Roger J. Stone Jr., a longtime Trump confidant who frequently advocates for the campaign on television, and Charles R. Black Jr. Mr. Kasich unveiled Mr. Black as an adviser earlier this month, in an announcement intended to convey his readiness for a contested convention – effectively making Mr. Black and Mr. Manafort, allies dating back to the 1970s, direct competitors in the 2016 race.”