Appearing on "Fox News Sunday," Durbin said Obama's political history adequately prepared the Democratic hopeful for the presidency.

"I think he's been tested and I think he's proven that he's used the right judgment on one of the most important foreign policy decisions in recent history," Durbin told host Chris Wallace of Obama's opposition of the Iraq war.

Sen. Diane Feinstein, D-Calif., was equally supportive of Sen. Hillary Clinton, D-N.Y., and her White House qualifications.

"It's the best experience anybody could possibly have that has not been a president of the United States," Feinstein said of Clinton's eight years as first lady.

Former White House senior adviser Karl Rove, meanwhile, said Sen. John McCain, R-Ariz., would have a battle on his hands if he faced the younger Obama in the general election.

"The question is can he make himself more -- can he make people more confident in his leadership and his experience and his ability than Obama can," Rove said of the Republican front-runner.