A Democratic senator on Wednesday called on US President Joe Biden to ditch his reelection bid, capping a brutal day that saw mounting pressure from high-profile actor and donor George Clooney and party heavyweight Nancy Pelosi. As the 81-year-old tried to show his leadership credentials at a NATO summit in Washington, domestic calls have been growing for Biden to quit following his disastrous debate performance against Republican challenger Donald Trump. At least eight House Democrats have openly called on Biden to not seek reelection, but Peter Welch became the first in the Senate to explici…