By Sam Youngman
WASHINGTON (Reuters) - Presidential candidate Mitt Romney unloaded on rival Republican Newt Gingrich on Tuesday on a liberal television network, comparing him to former candidate Herman Cain and others who have led the field briefly before flaming out.
"(Gingrich's) lead is not as much as it used to be," Romney said on MSNBC's "Morning Joe." "But that's sort of the process that other people have gone through."
"I suspect he'll lead until he doesn't lead," Romney said.
Former House of Representatives Speaker Gingrich's status as the Republican front runner to take on Democratic President Barack Obama in November's election is fading after weeks of attacks by rivals and intense media scrutiny of his political record and personality.
A poll on Monday put Gingrich in third place in Iowa, which kicks off the election cycle on January 3, behind U.S. Representative Ron Paul and Romney, the former Massachusetts governor.
Romney criticized Gingrich for remarks he made about Republican Representative Paul Ryan's plan to privatize the Medicare healthcare program for the elderly and an ad he did about global warming with former Democratic House Speaker Nancy Pelosi.
Romney said that on two of the biggest issues for conservatives, Gingrich sided with liberals.
"So for him to say he's more of a conservative is a bit of a stretch," Romney said. He said he thinks Gingrich will continue to fade as voters get to know more about him.
"There's a lot about Newt Gingrich that I didn't know," Romney said.
Romney, a candidate in the 2008 presidential election, said that at the beginning of this campaign he and his advisers thought winning Iowa "would be a real stretch."
While a win in Iowa followed by a win in New Hampshire, where Romney has consistently led, could give him enough momentum to cement the nomination early, Romney said he has raised the money and has the resources to compete until "the very, very end."
(Reporting By Sam Youngman; Editing by Vicki Allen)