John McCain, barely a year after he was the Republican nominee for president, faces a potential threat from within his own party as he gears up for his Senate re-election bid next year.

Former Rep. J.D. Hayworth, a Phoenix talk radio show host, is running neck and neck with McCain in a hypothetical matchup in a recent Rasmussen poll, even though Hayworth has not decided yet whether he will challenge McCain. The incumbent senator still holds a slight edge, with the support of 45 percent of poll respondents, compared to 43 percent for Hayworth.

"It's very humbling," Hayworth told FoxNews.com, adding that the poll has led to "a lot of in-depth discussion at the Hayworth hacienda."

"I think we all respect John as a historical figure," said Hayworth, who served in Congress from 1995 to 2006. "The question is, who can represent Arizona with a clear, consistent philosophy in the United States Senate. Apparently, the electorate, at least my fellow Republicans, are telling us in this poll they're inclined to look at someone other than John."

In a written statement, McCain's spokeswoman said, "Senator McCain never takes any election for granted and is working hard to continue to deserve the support of Arizonans as he fights to create jobs in the state and keep America safe."

Political experts in Arizona say the immigration issue, not an intraparty feud, is central to any struggles McCain may face. McCain's support for comprehensive immigration reform, including a pathway to citizenship for illegal immigrations already in the country, has hurt him politically in the past, including nearly derailing his presidential bid. Hayworth has derided such reform as amnesty for illegal immigrants.

"It's not a secret that Senator McCain has different feelings on immigration than Hayworth," said Matt Roberts, a spokesman for the Arizona Republican Party. "That's the issue garnering the most amount of attention and people feel strongly on both sides."

But some view the potential matchup as perhaps the next clash between conservatives and moderates fighting for the future of the GOP. In one such clash, a moderate Republican abandoned a race this fall for a congressional seat in upstate New York to make way for the Conservative Party candidate, though a Democrat eventually won that special election.

Hayworth said he doesn't view his potential entry into the race as part of an intraparty feud.

"Allowing Republicans to determine the standard bearer through a primary is a sign of a vibrant party, and I think it should be welcomed that Republicans (who) may have policy disagreements are willing to allow those disagreements and those preferences to be revealed through the primary process," he said.

Fred Solop, chairman of the political science department at Northern Arizona University, cast doubt on the accuracy of the Rasmussen poll, noting that it was an automated telephone survey that, he says, is under less control and can lead to varying results.

He also said McCain shouldn't lose sleep over the poll because the senator has amassed a huge war chest of nearly $30 million, while Hayworth is still weighing whether to run. But Solop added that other data indicate the race is tight.

"So I imagine this will be a high-profile race," he said, adding that immigration reform likely will be a hot topic next year after the debate over health care ends.

Hayworth wouldn't say when he'll make a decision on whether he'll enter the race, but he plans to continue discussing the prospect with his family.

"It's going to make the Thanksgiving conversation around the dinner table very, very interesting," he said.