Tom Vilsack, Ardent Clinton Supporter, Throws In The Towel:

(CNN) – Former Iowa Gov. Tom Vilsack, one of Hillary Clinton's most ardent supporters, said Sunday it's time for Hillary Clinton to acknowledge she has lost her bid for the Democratic nomination.

Vilsack, who was briefly a presidential candidate himself last year, told the Associated Press it's "pretty clear that Senator Obama is going to be the nominee."

"After Tuesday's contests, she needs to acknowledge that he's going to be the nominee and quickly get behind him," Vilsack also said.

Game over. Expect the pressure to increase through Wednesday.