Senate Democrats are poised to throw away 20 years of friendship and a bipartisan working relationship with Sen. Jeff Sessions to wreak political vengeance on him this week as they consider his nomination for attorney general. Highlighting the deep partisan divide and the bad blood between Democratic lawmakers and President-elect Donald Trump, the same senators who have socialized and co-authored reams of legislation with Mr. Sessions are under pressure from liberal interest groups to air accusations that he is a racist, a sexist and a homophobe. Mr. Sessions, who has held an Alabama seat in the Senate since 1997 and...