Sanders has the donors, Biden leads polls in Tuesday primary states

Sen. Cory Booker (D-N.J.) endorsed former Vice President Joe Biden on Monday in Michigan. (Photo by Mandel Ngan/AFP via Getty

Warren faces challenge from Sanders in home state despite financial backing

Senator Elizabeth Warren (JOSEPH PREZIOSO/AFP via Getty Images) After failing to make headway in key early primary states, polls suggest

South Carolina donors give the greatest amount to Biden as Sanders cuts into the lead

(Sean Rayford/Getty Images) Former Vice President Joe Biden is placing his bets on a state that is his stronghold, South

Biden dominates with Nevada donors ahead of caucus

(John Tlumacki/The Boston Globe via Getty Images) Democratic presidential candidates who received the greatest amount of  donations from Iowa and