U.S. Rep. Conor Lamb said Friday he is running for Pennsylvania’s open Senate seat, joining a crowded Democratic field in one of the nation’s most competitive races. Lamb is seeking the nomination to replace outgoing GOP Sen. Pat Toomey. Lamb, a former Marine and federal prosecutor, rose to political prominence three years ago when he beat a Donald Trump-backed Republican in a special election that foreshadowed the 2018 Democratic takeover of the House. The Senate race is wide open on both sides and is expected to be among the most expensive in the 2022 U.S. midterm election. Toomey is retiring after two terms.