"If you’re going to be president you have to have some discipline in how you approach things and how you assess situations," Harkin said. "Newt has never been one to engage mind before opening mouth. He engages mouth before engaging his mind sometimes, most of the time. That doesn’t bode well for him at all."

Harkin went on to describe "silent cheering in the Obama Administration and the Obama campaign for Newt to get the nomination."

"It would be just be heaven-sent if he got the nomination,” Harkin said.

The call was first reported by Radio Iowa.

Harkin's sentiments echoed that of outgoing Rep. Barney Frank (D-Mass.), who said that Gingrich's nomination "would be the best thing to happen to Democrats since Barry Goldwater."

"If Newt Gingrich is the nominee then ... wow," Frank said at the press conference announcing his retirement.

Harkin said Democrats were excited by the prospect of Gingrich winning the nomination, believing the former Speaker had lots of baggage that would be easily exploitable.

"Someone once described the prospect of Newt getting the nomination, saying that, ‘Imagine that you’re standing in front of a door and behind that door all these suitcases are piled and you open the door and all the suitcases come tumbling out.’  Of course, I didn’t know what they were talking about. He said, ‘Baggage, he has a lot of baggage and once he gets up there all that baggage comes tumbling out,'" Harkin said.

The Iowa senator said of Mitt Romney, the other Republican frontrunner, that the former Massachusetts governor has been "plodding" and "very cautious" thus far in the race.