HARRISBURG, Pa. — Republican David McCormick announced Thursday that he will make his second bid for U.S. Senate in swing-state Pennsylvania, this time to take on Democratic Sen. Bob Casey after losing in last year’s bruising and crowded Republican primary.

In a ballroom filled with supporters at the Heinz History Center in Pittsburgh, McCormick — who had floated the possibility of running again since last year — accused Casey of rubber-stamping harmful immigration, economic, energy and national security policies of President Joe Biden.

“When Joe Biden says ‘vote,’ Bob Casey says ‘which way?'” said McCormick, who left his job atop one of Wall Street’s best-known hedge funds to enter politics. “Bob Casey represents six more years of rubber stamps. … Do you know what Bob Casey is? Bob Casey is a rubber stamp that's been around too long.”

The Senate candidates in Pennsylvania will share a ticket with candidates for president next year in a state that is critical to whether Democrats can maintain control of the White House and the Senate.

A race between Casey and McCormick could be one of the nation's most expensive and closely watched in a year when Democrats have a difficult 2024 Senate map that requires them to defend incumbents in red states — Montana, Ohio and West Virginia — and multiple swing states.

McCormick entered last year's race for the seat being vacated by retiring Republican Sen. Pat Toomey and — after spending $14 million of his own money — ended up losing in the Republican primary to a Donald Trump-endorsed rival, celebrity heart surgeon Dr. Mehmet Oz. Democrat John Fetterman beat Oz in the November general election.

McCormick, 58, was heavily recruited to run again by the party establishment and, thus far, has a clear GOP primary field.

In a statement Thursday evening, Montana Sen. Steve Daines, who chairs the campaign arm of Senate Republicans and had urged McCormick to run, said McCormick had unified the party’s grassroots. He is “exactly the type of candidate” who can win in a competitive state like Pennsylvania, Daines said.

For months, Democrats have treated McCormick as Casey's de facto opponent, attacking his record in business, his opposition to abortion rights and indications that he still lives on Connecticut’s ritzy “Gold Coast ,” where he spent a dozen years as an executive at the hedge fund Bridgewater Associates.

Casey is unlikely to face serious opposition, if any, in his party's primary. He is a stalwart of Pennsylvania’s Democratic Party — the son of a former two-term governor and Pennsylvania's longest-ever serving Democrat in the Senate.

Casey is an key ally of labor unions and Biden. In Congress, Casey has backed all of Biden’s top priorities and forged a close relationship with the president, at least in part because the men both hail from the same hometown of Scranton.

Casey spent a decade in elected statewide office — as auditor general then as treasurer — before going on to win three elections for Senate by no fewer than 9 percentage points each time.

McCormick singled out Casey's long career in politics, saying he — and not Casey — is the kind of leader who will be able to shake up a broken Washington.

“I’m the only candidate in this race that can change Washington. … And frankly, my opponent is part of the problem,” McCormick said. “He first ran for office almost 30 years ago. Bob Casey's not going to change Washington. Bob Casey is Washington.”

McCormick, who grew up near Bloomsburg, is the son of Pennsylvania’s first state university system chancellor. He won a Bronze Star for his service in the first Gulf War and worked in Pittsburgh, where he ran online auction house FreeMarkets Inc. at the dawn of the tech boom.

He served in senior positions in former President George W. Bush’s administration before moving to Connecticut to work for Bridgewater.

He resigned as CEO and bought a house in Pittsburgh before running for Senate last year — although Democrats are seizing on his connections to Connecticut, including the $16 million mansion in Westport, where McCormick still spends considerable time.

“He doesn’t even live here,” Democratic Lt. Gov. Austin Davis said at a news conference Thursday. “He’s a mega-millionaire who lives in a mansion on Connecticut's Gold Coast.”

Democratic state Sen. Jay Costa, who represents the part of Pittsburgh where McCormick bought a house, said: “I know that he’s not there, because I work in that community day in and day out. … If you want to run for U.S. Senate, go to Connecticut and run for U.S. Senate in Connecticut, don’t come to be a carpetbagger here in Pennsylvania.”