On Wednesday afternoon, Sens. Mark Udall (D-CO), John Walsh (D-MT) and Kay Hagan (D-NC) all urged Shinskei to step down.
And by Wednesday night, Sens. Jeanne Shaheen (D-NH) and Al Franken (D-MN), both of whom are facing tough re-election battles, joined in calls for the secretary to resign.
"I have tremendous respect for General Shinseki and honor his service to this nation," Shaheen said in a statement. "However, it has become clear that after six years as head of the Department of Veterans Affairs, General Shinseki has been unable to solve other fundamental problems that plague the agency."