Trump's endorsements hailed as 'most powerful...in modern political history' after victories in OH, IL, CA

EXCLUSIVE – CLEVELAND – There were two winners in Ohio's Republican Senate primary – Bernie Moreno and former President Trump.

Moreno, a successful Cleveland-based business leader and luxury auto dealership giant, rode Trump's endorsement to victory in Tuesday's primary in a costly and contentious GOP nomination contest.

"I want to thank President Trump for all he did for me, for this campaign, for his unwavering support," Moreno said in his victory speech. 

Moreno, who highlighted that he spoke with the former president soon after his victory was projected, emphasized that "I wear with honor my endorsement from President Trump."

TRUMP'S SUPPORT HELPS PROPEL MORENO TO VICTORY IN BRUISING SENATE PRIMARY BATTLE

Republican Senate candidate Bernie Moreno celebrates with supporters after winning Ohio's GOP Senate primary in Cleveland on March 19, 2024. (Fox News/Paul Steinhauser)

Moreno's victory in a bruising primary battle over state Sen. Matt Dolan and Ohio Secretary of State Frank LaRose propelled him into a general election showdown against longtime Democratic Sen. Sherrod Brown in a race that may determine if Republicans win back the Senate majority in November.

The Senate primary in its closing days was framed as a showdown between Trump and the MAGA/America First wing of the party, which rallied around Moreno, vs. the conservative establishment, which supported Dolan. Additionally, it was partially viewed as a test of Trump's immense clout over the Republican Party.

WATCH: WHAT BERNIE MORENO TOLD FOX NEWS AFTER HIS PRIMARY VICTORY IN OHIO

Trump, who last week clinched the GOP presidential nomination as he became his party's presumptive 2024 nominee, easily cruised to victory in Ohio's Republican presidential primary on Tuesday.

However, Moreno's win in the competitive Senate contest was arguably a bigger victory for Trump than his presidential primary romp.

And it came on a night when Trump endorsed candidates won a handful of other contested GOP primaries in races across the country.

Republican presidential candidate former President Trump, right, greets Ohio Republican candidate for U.S. Senate Bernie Moreno during a rally at the Dayton International Airport on March 16, 2024, in Vandalia, Ohio. (Scott Olson/Getty Images)

"An endorsement from Donald J. Trump is the most powerful endorsement in modern political history," Moreno emphasized in an exclusive Fox News interview at his primary night celebration. "There's never been anything like it before – probably won't be anything like it afterwards."

He added that Trump's backing "was probably decisive" in his primary victory. 

"I think it was a victory for the [Trump] agenda. For the America First agenda," he added.

WILL REPUBLICANS IN OHIO REUNITE AFTER A BRUISING PRIMARY?

Dolan, who did not seek Trump's support, told reporters after conceding that "I think it's pretty self-evident that Donald Trump's endorsement for Bernie Moreno was a key factor for Bernie winning."

Ohio Gov. Mike DeWine, right, greets Ohio state senator and Republican candidate for U.S. Senate Matt Dolan during a campaign event in Columbus, Ohio, Monday, March 18, 2024. (AP Photo/Paul Vernon)

Trump was aiming for a repeat performance in Ohio.

Two years ago, the former president backed now Sen. JD Vance in a crowded and combative Republican Senate nomination race, boosting Vance to victory in the 2022 primary a couple of weeks later. That primary also included Dolan and Moreno, who dropped out a couple of months ahead of the primary after meeting with Trump.

Fast-forward to the present, and Trump returned to Ohio this past weekend after Dolan surged in the polls and landed the endorsement of two-term Ohio Gov. Mike DeWine and former Sen. Rob Portman, part of the state's Republican old guard.

Trump, at a rally outside Dayton, claimed that Dolan was a "weak RINO" [a derogatory acronym which stands for "Republicans in name only"] and charged that the state senator is "trying to become the next Mitt Romney."

Former President Trump speaks during a rally for Bernie Moreno in Vandalia, Ohio, on March 16, 2024. (KAMIL KRZACZYNSKI/AFP via Getty Images)

Romney, the 2012 GOP presidential nominee and establishment Republican senator from Utah, is reviled by Trump and the MAGA movement.

Moreno was also joined on the campaign trail in the closing days by two top Trump allies – Vance and Arizona Senate candidate and 2022 gubernatorial nominee Kari Lake.

In the end, the support from Trump and team MAGA helped boost Moreno to a double-digit victory over Dolan, with LaRose a distant third.

GOP Sen. JD Vance of Ohio, left, campaigns on behalf of GOP Senate candidate Bernie Moreno as they speak with party activists in Independence, Ohio, on March 19, 2024. (Fox News - Paul Steinhauser)

Moreno was not the only Ohio Republican boosted by Trump.

This past weekend, the former president endorsed state Rep. Derek Merrin in the GOP primary in Ohio's 9th Congressional District. On Tuesday, Merrin was the projected winner over former state Rep. Craig Riedel.

With the departure of controversial candidate J.R. Majewski from the primary earlier this month, Republicans are hoping Merrin can defeat veteran Democratic Rep. Marcy Kaptur in November.

"Donald Trump is the most important endorsement in Ohio, bar none," longtime Republican strategist and 2016 Trump campaign veteran Mike Biundo told Fox News on the eve of the Ohio primary.

Biundo, who has worked on multiple campaigns in Ohio, emphasized that "Trump moves numbers and helps to hand victories to those he endorses. It’s just a fact. Just look at Sen. JD Vance. He owes his seat to the last minute Trump endorsement."

The Trump endorsed candidate also came out on top in a contested GOP House primary in Illinois, where Rep. Mike Bost edged past former state lawmaker and 2022 gubernatorial candidate Darren Bailey.

And Vince Fong, endorsed by Trump and former House Speaker Kevin McCarthy, was leading at last check in a special election to fill McCarthy's vacant congressional seat in California.

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However, Trump's endorsement record in contested Republican primaries is not perfect.

"This is Trump's party and his endorsement in contested primaries has proven to be helpful, but it's not a lock," veteran Republican strategist and communicator Ryan Williams noted.

An Ohio-based Republican consultant, who asked to remain anonymous to speak more freely, last week called the Republican Senate primary "a litmus test" of Trump's sway over the GOP.

"The real question is whether President Trump's endorsement still carries weight with Republican primary voters in Ohio," the consultant said. "It's that simple and straight forward, and I think ultimately the answer is yes."

Fox News' Jamie Vera, Deirdre Heavey and Brooke Curto contributed to this report.

Get the latest updates from the 2024 campaign trail, exclusive interviews and more at our Fox News Digital election hub.