[cnn-photo-caption image= http://i.cdn.turner.com/cnn/2008/images/06/02/art.vilsack.ap.jpg caption="Vilsack is a strong supporter of Hillary Clinton."](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.
Vilsack first announced he was running for president in November, 2006, but dropped his bid three months later after the Democrat failed to drum up a significant level of support or raise the necessary campaign funds needed to compete. He endorsed Clinton shortly after and played a key role in the New York senator's unsuccessful Iowa campaign effort.
His comments came the same day the Clinton showed signs she plans to press on after Tuesday's contests - continuing argue she has won the popular vote and that the party's superdelegates are able to switch their allegiances before the convention in August.