“He has revealed the Deceit, Corruption, and outright Theft of the 2020 Presidential Election, and will do something about it. He will also Fight Violent Crime, Strengthen our Borders, Protect Life, Defend our under-siege Second Amendment, and Help our Military and our Vets. He is a fighter like few others, and has been with me right from the beginning, and now I have an obligation to be with him,” Trump continued.

Mastriano — who also has ties to the QAnon conspiracy theory — was already leading in the polls in the fractured primary, despite being well outspent on TV by candidates like former U.S. Attorney Bill McSwain and businessman David White.

Trump called Mastriano on Friday to inform him of his decision to endorse, according to a person familiar with the call.

But the decision came following pushback from some of Trump’s closest advisers and allies, among them Fox News host Sean Hannity.

Trump had been skeptical of Mastriano, according to another person familiar, but was impressed by his lead in the polls and focus on the 2020 election.

“I’m honored to receive the endorsement from President Trump, today. But the honor is not for me. It’s for the millions of hard-working Pennsylvanians who want their individual liberties restored, power returned to the people, and for their elected leaders to fulfill the America First — and Pennsylvania First — agenda,” Mastriano said in a statement.

Presumptive Democratic nominee for governor Josh Shapiro has been encouraging Mastriano’s candidacy in ads, believing he is the easiest Republican to beat in a general election. “Shapiro just became the next governor and I don’t mean that hyperbolically,” one top Pennsylvania GOP aide said.

Top Republicans this week mounted a last-ditch effort to stop Mastriano from winning the party nomination in the May 17 primary. But those efforts have seemingly failed. Some now-former candidates polling in the single digits have dropped out and endorsed former Rep. Lou Barletta in recent days, including state Senate President Jake Corman. But the split at the top of the field, combined with Mastriano’s new endorsement from Trump, will likely doom that effort.

“At the end of the day, a Trump endorsement could get you a few points and that might be all you need [in a crowded primary]. A point or two could be all the difference for a candidate coming down the stretch,” Brian Nutt, a Republican strategist in Pennsylvania, said earlier this month.

Trump’s endorsement of Mastriano could also complicate the Senate primary in the state as well. Trump has thrown his support behind Mehmet Oz, known as “Dr. Oz,” in another crowded field. But Mastriano has aligned himself with Kathy Barnette, another far right candidate who has similarly surged in the polls. Barnette and Mastriano often campaign together, and have endorsed each other.

Barnette, Oz and hedge-funder Dave McCormick have been locked atop recent polls in the Senate primary, while Lt. Gov. John Fetterman seems to be on a glide path to beating Rep. Conor Lamb and others in the Democratic primary.

Some Republicans close to the former president have argued that Trump backing Mastriano could backfire by hurting Oz. “People have been telling the president for a while, and he’s not protecting his Oz investment” in the governors’ race, another Republican close to Trump said.

Craig Howie contributed to this report.