WASHINGTON (CNN) -- Former Senate Democratic Leader Tom Daschle will not seek his party's presidential nomination in 2008, a senior political advisor told CNN Saturday night.

"After many months of looking at a possible run for the presidency, he has decided not to seek that office in 2008," Steve Hildebrand, Daschle's political advisor, said in an interview.

Daschle had visited the early proving grounds of Iowa, New Hampshire and Michigan earlier this year as he considered a possible bid for the White House. The South Dakotan seriously considered seeking the Democratic presidential nomination in 2004, but ultimately decided to seek another term in the Senate. He was defeated by former Republican Rep. John Thune.

Hildebrand said Daschle made the decision after seeing that Democrats were in a better position following the midterm elections "to affect change in Washington and also better positioned to win the White House in 2008." Hildebrand also said that the estimated $50 million some analysts predict will be needed to compete in the Democratic primary was another reason why Daschle chose not to run.

"It is a very daunting and difficult process," Hildebrand said of the enormous amount of money a candidate needs to be viable.

While Daschle's inner political circle remained very loyal to him, several of them are working or advising other candidates. Hildebrand is an unofficial advisor to Sen. Barack Obama, D-Illinois, who is considering a presidential bid. Obama's chief-of-staff Pete Rouse held the same position for Daschle. And Daschle's former communications director Todd Webster has created a draft Obama website urging him to seek the Democratic presidential nomination. Meanwhile, Daschle's media strategist Anita Dunn and former communications expert Dan Pfeiffer are advising Sen. Evan Bayh, D-Indiana, who will announce this week the formation of a presidential exploratory committee.

Daschle is a special policy advisor for the law firm Alston & Bird and is also affiliated with the Center for American Progress, a progressive think-tank.