NEW YORK (AP) — Democratic operatives believe that Joe Manchin’s decision not to seek reelection virtually ensures the party will lose his Senate seat next year in deep-red West Virginia. At the same time, some Democratic officials are concerned that Manchin’s announcement frees him to pursue a third-party presidential bid. Some think Manchin might ultimately undermine President Joe Biden’s reelection. Overall, his announcement injects a new layer of uncertainty for Democratic leaders already anxious about the party’s prospects in 2024. Biden is seeking a second term despite persistent concerns about his age and economic leadership. And Democrats are clinging to a one-seat majority in the Senate.