With his campaign seemingly running on empty, GOP presidential candidate Newt Gingrich acknowledged Friday that rival Mitt Romney is clearly in the lead and likely will get enough delegates to win the party’s nomination.

“I think Mitt Romney is clearly the front-runner,” Gingrich said while campaigning in Wisconsin ahead of the Tuesday primary. “I think he will probably get 1,144 (delegates), but I think he has to earn it.”

Even so, the former House Speaker refuses to leave the race, saying Friday and he has said before that he’ll continue his campaign until Romney gets enough delegates.

"I am comfortable that the day (Romney) gets 1,144 delegates, we will all unify and support him,” Gingrich told WTMJ News Radio. “But he has to finish earning the delegates, and that’s how the process goes.”

Gingrich's campaign has tried to keep pace this year with support from Las Vegas billionaire Sheldon Adelson. But with Gingrich running a distant third to Romney and former Pennsylvania Sen. Rick Santorum in most polls, Adelson suggested Thursday that he will stop financing Gingrich’s now long-shot bid.

"It appears as though he’s at the end of his line,” Adelson said. “Because, I mean, mathematically, he can’t get anywhere near the numbers, and it’s unlikely to be a brokered convention.”

Earlier this week, a Gingrich spokesman announced the campaign would start charging $50 for a photo opportunity with the candidate, another sign of financial trouble.

Just 8 percent of likely voters in the Wisconsin primary said they would vote for Gingrich, putting him behind Romney, Santorum and Texas Rep. Ron Paul, according to an ABC/Marist poll released Friday.

There are 42 delegates up for grabs in the winner-take-all primary in this Midwestern swing state.

The overall delegate count is now 568 for Romney, 273 for Santorum, 135 for Gingrich and 50 for Paul, according to the Associated Press.

Gingrich has won only two primaries, South Carolina and Georgia, which he represented in Congress for 20 years.

Romney, a former Massachusetts governor, picked up a key endorsement Friday from Wisconsin GOP Rep. Paul Ryan, the powerful chairman of the House Budget Committee.

Gingrich said later in Green Bay that he and wife, Callista Gingrich, would "obviously" support Romney.

"And I'm sure Santorum will support him," he said."If Romney does get 1,144, I'll be glad to help him defeat Obama."

Gingrich said he, Romney and Santorum mutually support one another in making sure Obama is not re-elected.