Sen. Bob Casey’s (D-Pa.) reelection announcement has teed up what is expected to be one of the most closely watched Senate races going into 2024.

Republicans view Casey as vulnerable and are hoping to improve on candidate quality this time around with former Senate candidate Dave McCormick.

However, former failed conservative gubernatorial candidate Doug Mastriano is eyeing another potential run, raising alarm for the GOP.

With Casey in, the attention now shifts across the aisle where Republicans hope to avoid a 2022 redux as Mastriano prepares a bid for the seat. One Pennsylvania-based GOP operative told The Hill that Mastriano is “getting every single duck in a row” ready for a potential run, noting that he’s been firing up his Facebook Live events that he frequently held during the 2022 campaign.

“He’s doing everything in his power to consolidate his base and to make sure they’re staying with him in the event that he runs,” the operative said.

Mastriano lost the race for the governor’s mansion in Harrisburg to now-Gov. Josh Shapiro (D) by nearly 15 percentage points.

Despite the state senator’s high floor with potential primary voters, GOP operatives are bullish that 2024 will not be a redux of last year’s primary issues, both on the gubernatorial and Senate side, especially if the race is a head-to-head match-up between him and McCormick.

The well-funded ex-hedge fund CEO spent more than $14 million on last year’s Senate primary contest in roughly five months. By contrast, Mastriano was outspent 30 to 1 by Shapiro and received little outside financial support.

Adding to Mastriano’s troubles, the financial burden would be more problematic in a McCormick hypothetical match-up as he would no longer be able to raise unlimited sums of money as candidates for governor are able to do. Senate races are subject to Federal Election Commission limits.

“Doug couldn’t raise any money to talk to any of the voters outside of Facebook Lives. How’s he going to do it when there’s actual limits?” a second Pennsylvania-based GOP operative said, adding that Mastriano would likely start with 25- to 28-percent support in a primary now. “But how do you get to 50 percent if it’s a two-person thing? You’ve got to be able to talk to people and advertise.”

Mastriano’s potential entrance has also heightened the push for McCormick allies to push him into the race. The 2022 Senate candidate has said in recent radio interviews that he is still undecided on a bid.

“It’s reinvigorating the McCormick people,” the first operative said, adding that they’ve “gone from asking him to run to begging him to run.”

The party apparatus has already lined up in support of McCormick if he runs. Sen. Steve Daines (Mont.), chairman of the Senate GOP campaign arm, and the Senate Leadership Fund, which is run by allies of Senate Minority Leader Mitch McConnell (R-Ky.), have both signaled their backing.

Democrats, on the other hand, are salivating at the thought of a Mastriano-versus-McCormick primary match-up.

“It’s going to be a fairly nasty primary and whoever comes out of that is going to be damaged,” said one Pennsylvania Democratic operative. “In order to win a Republican primary in Pennsylvania these days it seems like you really have to go far to the right and then that hurts you in the general.”  

And Mastriano’s recent Facebook Lives seem to suggest that the former gubernatorial candidate is priming himself for a battle against McCormick. In a recent appearance, Mastriano argued that moderate candidates are lacking support from conservative segments of the primary electorate and that there’s “no guarantee that they’re going to have us.”

It’s a similar argument Democrats make too as they point to McCormick’s vulnerabilities, noting his loss to Oz in last year’s GOP Senate primary. McCormick fell short of Oz by just under 1,000 votes.

“The one thing I will say about McCormick is that Dr. Oz was a particularly bad candidate but McCormick lost to him, so that says something about McCormick,” the Pennsylvania Democratic operative said.

The Democratic Senatorial Campaign Committee (DSCC) echoed this in a statement to The Hill.

“For months, Pennsylvania Republicans savaged McCormick over his record of outsourcing jobs and for his close ties to China, Wall Street and Mitch McConnell,” said spokesperson David Bergstein. “With Mastriano making noises about entering the race, Republicans’ Senate primary dynamics are getting messier by the day.”

The Pennsylvania Democratic operative added that no matter who comes out of the GOP primary, Casey’s allies are “confident” his record will withstand a challenger.

At the end of the line for any Republican is, of course, Casey — the three-term senator who dethroned a member of Senate GOP leadership to win his seat in 2006 and who the party has struggled mightily at challenging in his previous two reelection bids.

While Casey is far from being one of the loudest voices in the Senate Democratic caucus, multiple GOP operatives argue that taking him down will still be no small feat and that the party likely needs a royal straight to do so.

“He’s the Pennsylvania politician with the greatest name-ID that ever existed. You can’t buy better name-ID,” the first Pennsylvania-based GOP operative said. “I think that Casey is beatable with the right candidate, the right amount of money, the right political climate and a renewed sense of wanting new leadership, and I think you need every single one of those situations to occur to defeat him.”

“He’s got everything going for him,” the operative added about the Scranton-based Democrat.

President Biden, who is expected to be at the top of the ticket next year, will also likely be a key player in the race.

“President Biden has not kept his feelings about Pennsylvania a secret,” the Pennsylvania Democratic operative said.

“When Biden comes and talks about the accomplishments that he and Sen. Casey have gotten done, they’re the same kinds of things that Sen. Casey is talking about every day in Pennsylvania.”