Republican David McCormick — his party's runner-up in the 2022 Pennsylvania Senate primary — raised $5.4 million in his first quarter as a 2024 candidate, according to the campaign.

Why it matters: The early influx of cash into McCormick's campaign and joint fundraising committee is the latest sign that Pennsylvania's Senate race will be among the nation's most competitive contests in November, with control of the U.S. Senate potentially hanging in the balance.

• McCormick, a former CEO of the Bridgewater Associates investment firm, also contributed $1 million of his own money in the fourth quarter of 2023 to boost his bid to oust three-term incumbent Sen. Bob Casey (D-Penn.).
• McCormick has been endorsed by the entire Pennsylvania GOP congressional delegation, which could help him avoid the kind of nasty primary that left Trump-backed TV personality Mehmet Oz bruised before the 2022 general election, which he lost to Sen. John Fetterman (D-Pa.).

What they're saying: "Dave McCormick has earned the support of Pennsylvanians from all walks of life because he is a proven leader who can address the burden of inflation on working families, push for a secure border, and protect the security of Americans at home and abroad," Matt Gruda, McCormick's campaign manager, said in a statement to Axios.

The other side: Casey, from a family with a storied name in Pennsylvania politics, raised $3.2 million in the third quarter of 2023, the last numbers that are publicly available.

• He had his best quarterly fundraising total in 18 years in the second quarter, raising more than $4 million.
• Quarterly fundraising reports for the fourth quarter are due to the Federal Election Commission in mid-January, but some candidates — such as McCormick, who began his campaign in September — announce their fundraising figures ahead of time, especially when they’re pleased with their numbers.

Zoom out: Along with contests in Montana and Ohio, the Pennsylvania race could determine the control of the Senate, where Democrats now have a razor-thin margin.

• Democrats are defending Senate seats in Montana, West Virginia and Ohio — states that former President Trump won in 2020.
• With Sen. Joe Manchin's (D-W.Va.) retirement, Democrats aren't confident they will retain the West Virginia seat, meaning Republicans have to flip only one other seat to take the majority.
• But Democrats will have plenty of cash to help execute their battle plans.
• For seven Senate seats that Democrats currently control, their candidates brought in a total of $21.6 million from July through September, ending the second quarter with a combined $67.2 million in their accounts, according to NBC News.

Zoom in: Pennsylvania, where last week President Biden gave a major address to attack Trump for his role in the Jan. 6 attack on the Capitol, will be front-and-center throughout 2024.

• Biden won the state by some 80,000 votes in 2020, snatching it back from Trump, who surprised Hillary Clinton there in 2016.
• Biden's approval rating has been below 40% in the state and is frequently in a statistical tie just 34% in a December survey, according to surveys.
• An October Quinnipiac poll on the Senate race had Casey leading 50–44, with McCormick ahead with independents, 45–44.

The bottom line: Money alone isn't going to decide Pennsylvania's Senate race. Outside Super PACs also will flood the expensive Philadelphia and Pittsburgh airwaves.

• But McCormick's first fundraising numbers are a clear sign that GOP donors across the country like his chances.