Decorated combat veteran and 2020 Republican congressional candidate Sean Parnell is expected to launch a Senate campaign on Tuesday in the 2022 race to succeed retiring GOP Sen. Pat Toomey in the key battleground state of Pennsylvania.A source close to Parnell told Fox News that it’s “expected” that he will announce he’s running for Senate.KNOW MORE ABOUT PENNSYLVANIA’S SEAN PARNELL And Parnell has scheduled what’s being billed as a “special event” for 5pm ET in McCandless, Pennsylvania, in his home base in Pittsburgh’s northern suburbs in the western part of the Keystone State.The open seat battle in Pennsylvania is one of just a handful of races that will likely decide whether the Democrats retain their razor thin Senate majority or if the GOP regains control of the chamber in next year’s midterms – which will also greatly influence how much President Biden would be able to accomplish in the final two years of his current term in the White House.Parnell, who earned a Bronze Star and a Purple Heart while serving as an Army Ranger in the war in Afghanistan, ran for Congress last year, winning the support of then-President Trump and speaking at last summer’s Republican National Convention.He raised roughly $4 million in a race that grabbed national attention, but ended up narrowly losing to incumbent Democratic Rep. Conor Lamb last November in Pennsylvania’s 17th congressional district, which is located north and west of Pittsburgh.TRUMP ALLIES AIMING TO REPLACE RETIRING OLD GUARD GOP SENATORSParnell was also one of the lead plaintiffs in a unsuccessful lawsuit that attempted to reverse now-President Biden’s narrow victory over Trump in Pennsylvania. Parnell is friends with the former president’s eldest son, Donald Trump Jr., who tweeted in February that “My friend @SeanParnellUSA is a strong America First conservative and has my support for any office he decides to run for in 2022!!!”Fox News has confirmed that Parnell recently met with GOP leaders in the nation’s capital, including Sen. Rick Scott of Florida, the chair of the National Republican Senatorial Committee, which is the re-election arm of the Senate GOP.And this past weekend, Parnell spoke at a county GOP committee spring dinner in Luzerne County, in the northeastern corner of Pennsylvania, on the other side of the state and from his home base.PENNSYLVANIA DEMOCRATIC LT. GOV. FETTERMAN JUMPS INTO SENATE RACE Parnell will become the latest Republican to jump into the Senate race. Among those already in are former candidate for lieutenant governor and real estate developer Jeff Bartos, former congressional candidate Kathy Barnette, and self-described whistleblower Everett Stern. Former Navy Secretary Kenneth Braithwaite and former U.S. Ambassador to Denmark Carla Sands are among those mulling bids.In the race for the Democratic Senate nomination, Lt. Gov. John Fetterman, state Rep. Malcom Kenyatta, and Montgomery County commissioner Val Arkoosh have already launched campaigns, with Lamb and state Sen. Sharif Street seriously eyeing bids.The Senate is split 50-50 between the two parties, but the Democrats hold a razor-thin majority due to the tie-breaking vote of Vice President Kamala Harris, who serves as president of the Senate. That means the GOP only needs a one-seat pickup to regain the majority.CLICK HERE FOR THE FOX NEWS APPRepublicans are defending 20 of the 34 seats up for grabs in 2022, including open seats in battleground North Carolina and three other states, besides PennsylvaniaBut Republicans see potential pickup opportunities in the key battlegrounds of Arizona, Georgia, Nevada, and New Hampshire.