 Biden's candidacy. More from Lisa Taylor. Senior advisors Mike Donilon, Steve Ruschetti, and Biden campaign chair Jan O'Malley Dillon will join a special caucus lunch meeting at the Democratic Senatorial Campaign Committee. The meeting comes after Democratic Senators John Tester, Sherrod Brown, and Michael Bennett have said they think Biden will lose to Donald Trump in the general election and hurt the party's chances of holding the Senate. Tester and Brown are two of the most vulnerable Senate Democrats. A handful of House Democrats, meanwhile, have called on Biden to drop out of the race.