Sean Parnell forewarned during an interview on Breitbart News Saturday that Democrats would aggressively dig for information to use to attack whoever wins Tuesday’s Republican Senate primary in the battleground state of Pennsylvania.

Parnell, a former Senate candidate who is backing businessman David McCormick in the primary, said McCormick would be the GOP candidate most able to withstand those forthcoming attacks in a general election race that could very well decide which party holds the Senate majority next year.

McCormick “is by far the most qualified candidate. He’s eminently qualified,” Parnell said.

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Parnell emphasized how critical it would be for Republicans to choose McCormick, who is competing in what has become a tight three-way race against Dr. Mehmet Oz and Kathy Barnette.

“If you’re now a contender for the most important Senate seat in the country — legitimately, the balance of power in the Senate this cycle passes right through the heart of Pennsylvania — and what a lot of Republicans don’t perhaps think about enough … Republicans focus on campaigning. Democrats focus on elections, and I think the radical left is far better at looking at the big picture than maybe some Republicans, than Republicans are,” Parnell said.

He added, “And what I mean by that is that the Democrats see Pennsylvania as the bellwether for the entire country for the presidency in ’24, so they know going into this race, right, that whatever party wins this race in ’22 makes it far more likely for that party to win in ’24. So that’s why you’re seeing this race as just a no holds barred, like bare knuckle fight, like look at what happened to me with my custody trial and all of that stuff. They are out. Democrats are as cutthroat as humanly possible.”

Parnell, who had been endorsed by former President Donald Trump, had widely been considered the frontrunner in the Senate primary before he was forced to drop out amid a public and bitter custody battle with his estranged wife. Trump then decided to endorse Oz, who shares Trump’s celebrity TV background.

After Parnell’s exit from the race, Oz and McCormick became the two frontrunners in the packed primary field, and the pair have been far and away the top two GOP fundraisers and spenders in the race.

Barnette, however, saw a last-minute surge in polls following the last Senate debate, leading to a rush of media coverage about her background and qualifications.

The past week became dominated with questions about if she served a full ten years in the military like she said she did, if she could explain incendiary tweets she once shared seven or eight years ago, and why a discrepancy exists about if she voted for Trump in 2016.

Parnell, a decorated military veteran, said he was particularly interested in getting to the bottom of her military service through various verification forms that could be confusing to the average voter. He also noted certain past tweets of hers, like saying “pedophilia is a cornerstone of Islam,” would not set well with Pennsylvania’s many independent voters.

“In Pennsylvania, the Democrats have a 585,000-person voter registration advantage. There are 1.2 million independents in the state of Pennsylvania. You simply cannot win this state without some crossover appeal and having the right message to bring independents to your cause,” Parnell said. “Like Oz, I’m sure he’s a real nice guy, but he’s a liberal. People in this state perceive him as a liberal. They’re not going to rally to his cause. God forbid if Kathy squeaks this thing out, which I don’t think that she will, but if she does, you need more than just conservative Republicans to win Pennsylvania, and some of the things that she said are just, are just crazy. I’m sorry. They’re just crazy.”

Vouching for McCormick, Parnell added, “Dave is the guy that’s constant, has been consistent in all of his positions. He’s a combat veteran. He’s a business leader. He understands what it means to live the American dream. In this state, if you live in Pennsylvania, you need to rally around this man and help us sprint to the finish.”

Write to Ashley Oliver at aoliver@breitbart.com. Follow her on Twitter at @asholiver.