EXCLUSIVE - As he runs for re-election in a crucial 2024 Senate showdown that may determine if Republicans win back the chamber's majority, longtime Democratic Sen. Sherrod Brown's coming under a new attack over border security, the drug crisis, and crime.

Former prosecutor and Republican state lawmaker Matt Dolan, who's one of the two major Republican candidates running to challenge Brown next year, is launching a major ad blitz in Ohio targeting the incumbent senator.

"Liberal Sherrod Brown votes with Joe Biden 98% of the time. They’ve opened our borders, created the worst violent crime in decades, and allowed fentanyl to pour into Ohio communities," charges the narrator in the spot, which was shared first with Fox News on Tuesday.

Dolan's campaign says they'll spend seven-figures to run the ad statewide on TV and digital.

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The commercial includes a clip of Dolan at the nation's southern border, where he argues that Brown touts his record, saying "as a prosecutor, I locked up drug dealers and violent felons. In the state Senate, I voted to designate the cartels as terrorist organizations."

Dolan - who was joined by some members of Ohio law enforcement during an April trip to the Tucson Sector in Arizona, which is one of the busiest border sectors in both apprehensions and narcotic seizures - charges that "Sherrod Brown isn’t willing to fight, but I am."

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And if elected to the Senate, Dolan pledged in a statement to Fox News that "I will take the necessary steps with infrastructure, civilian and military personnel to stop the flow of human trafficking and fentanyl into the country, save American lives and restore our nation’s sovereignty."

Matt Dolan at nation's southern border with Mexico

Republican Senate candidate in Ohio Matt Dolan (center) tours the Tucson, Arizona sector of the U.S.-Mexico border, on April 3, 2023. (Matt Dolan campaign )

Dolan, who's also a former Ohio assistant attorney general, is making his second straight bid for the Senate. Last year, he was the Senate candidate who was the biggest surprise as he surged during the closing weeks of Ohio’s crowded and combustible 2022 Republican nomination race.

While much of the crowded and combustible field of Republican Senate candidates in Ohio last cycle showcased their loyalty to former President Donald Trump (who won Ohio by eight points in his 2016 presidential election victory and 2020 re-election defeat) and took aim at each other, Dolan kept his distance from both the crossfire and from Trump while showcasing his conservative credentials and agenda.

Dolan — whose family owns Major League Baseball’s Cleveland Guardians — also shelled out millions of dollars of his own money to run ads for his Senate bid. He surged near the end of the primary race, winning 23.3% of the vote, just behind former state Treasurer Josh Mandel at 23.9%. Former hedge fund executive and best-selling author JD Vance won the early May primary with 32.2% of the vote, thanks in part to a last-minute endorsement from Trump. 

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As Fox News was first to report, now-Sen. Vance last month endorsed Bernie Moreno, the other major Republican Senate candidate in the 2024 Senate race. The Cleveland based business executive is also making his second straight Senate run. Moreno ended his first Senate bid a couple of months ahead of the primary.

Ohio Secretary of State Frank LaRose is also seriously mulling a 2024 Republican Senate bid.

Sen. Sherrod Brown, D-Ohio, speaks to reporters in the Senate subway on his way to a vote at the U.S. Capitol March 14, 2023 in Washington, D.C.

Sen. Sherrod Brown, D-Ohio, speaks to reporters in the Senate subway on his way to a vote at the U.S. Capitol, on March 14, 2023, in Washington, D.C. (Drew Angerer/Getty Images)

The winner of next year’s GOP primary will challenge Brown, who’s the only Democrat to win statewide in Ohio in the past decade. Brown is being heavily targeted by Republicans in a state that was once a premiere battleground but has shifted red over the past six years.

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Democrats currently control the Senate with a 51-49 majority, but Republicans are looking at a very favorable Senate map in 2024 with Democrats defending 23 of the 34 seats up for grabs. Three of those seats are in red states that Trump carried in 2020: Ohio, Montana and West Virginia. Five others are in key swing states narrowly carried by Biden in 2020: Arizona, Michigan, Nevada, Pennsylvania and Wisconsin.