Former House Speaker Newt Gingrich predicted he would win in two crucial Southern primaries Tuesday, and blasted Mitt Romney as the Republican Party’s weakest presidential candidate since 1920.

“Yes, he’s the front-runner,” Gingrich said during an appearance on Fox News Sunday. “He is not a very strong front-runner. Almost all conservatives are opposed to him.”

"The Mitt Romney camp has been trying to sell, since last June, that I should get out of the race and that Romney is inevitable. But the fact is, Romney is probably weakest Republican front-runner since Leonard Wood in 1920, and Wood lost on the 10th ballot."

Gen. Leonard Wood sought the party’s nomination in 1920. Wood lost the nomination during a brokered convention, clearing the way for Warren G. Harding, who is often faulted for deepening a recession and whose administration saw several scandals.

Gingrich faces a pivotal test in Tuesday's primaries in Mississippi and Alabama. The GOP hopeful has staked his candidacy on a strong showing in Southern states.

Gingrich said he expects to win both primaries and stood by his vow to stay in the race through the convention.

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"I think we'll win both. We are campaigning very aggressively in both states," he said. "As almost everywhere, you start a little behind because of Romney's money and the length of time he's advertising. And as you campaign, you catch up with him pretty rapidly, and I think we're probably polling ahead in both states right now."

Gingrich also brushed off suggestions that it’s time for him to drop out of the race because he would need to capture huge percentages of the remaining delegates in order to challenge Romney’s lead.

“I think there’s a space for a visionary conservative,” he said.

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Gingrich also insisted that his decision to stay in the GOP race will not hurt Republicans in the general election.  

“It didn’t seem to hurt Barack ObamaBarack Hussein ObamaAll five living former presidents to attend hurricane relief concert Overnight Health Care: Schumer calls for tying ObamaCare fix to children's health insurance | Puerto Rico's water woes worsen | Dems plead for nursing home residents' right to sue Interior moves to delay Obama’s methane leak rule MORE to have a vigorous contest. He won the election, remember?” Gingrich said on CBS’s “Face the Nation,” referring to the heated 2008 primary with Obama and Hillary ClintonHillary Diane Rodham ClintonChris Murphy’s profile rises with gun tragedies DNC, RNC step up cyber protections Gun proposal picks up GOP support MORE.

The former Speaker holds the lead according to an American Research Group poll in Mississippi with 35 percent support to Romney's 31 percent. Polls show Gingrich, Romney and Rick Santorum all in a dead heat in Alabama.

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Andrew Restuccia contributed.

This story was posted at 8:49 a.m. and has been updated.