Promising poll numbers and new arrivals in the state are convincing North Carolina Democrats that Sen. Elizabeth Dole (R-N.C.) could be ripe for an upset.

But with no credible Democratic challengers stepping forward, Republicans — and even some Democrats — are calling the theory purely academic.

“We have stopped counting the number of people who have said no to [Democratic] recruitment attempts,” said National Republican Senatorial Committee spokeswoman Rebecca Fisher.

Although it’s still four months out from North Carolina’s filing deadline, popular Democratic Rep. Brad Miller and Gov. Mike Easley (D) have dashed party hopes of increasing the majority in the Senate next year with the victory in the Tar Heel State.

Some Democrats also had hoped to convince one of the party’s two leading candidates for governor in 2008, state Treasurer Richard Moore and Lt. Gov. Bev Perdue, to run for Senate, but neither has abandoned the gubernatorial race.

Easley, who is concluding his second term, won “in good times and bad,” according to one prominent Democratic source in the state, who said the governor would be “the strongest candidate” to challenge Dole in 2008. But there’s just one caveat, the source said: “He has not led on that he has an interest … every indication is that he’s not available.”

Earlier this summer, Miller told Democratic Senatorial Campaign Committee Chairman Charles Schumer (N.Y.) that he will not take on Dole next year. Miller’s decision appeared to set off Democratic grumblings of a squandered Southern pickup opportunity-in-the-making — misplaced frustration, some Democrats say, brought on by overly optimistic poll results.

Earlier in the year, a poll from the Democratic firm Garin-Hart-Yang Research Group suggested that only 35 percent of voters would re-elect Dole. The study, conducted Feb. 7-8, surveyed 606 likely voters. An Elon University poll three months later suggested that about half of adults approved of Dole’s job performance, while 10 percent disapproved of the job she was doing.

But now some Democrats privately doubt the accuracy of earlier polls showing a pickup opportunity, claiming that only a down-and-dirty campaign will determine the full extent of the Senator’s vulnerability. Last week, a Dole campaign poll of 500 likely voters showed her approval rating at 64 percent. The survey had a 4.4 point margin of error.

“I don’t see that Elizabeth Dole has offended the voters of North Carolina,” one state Democratic source said. “I don’t see that her negatives are high, but a campaign could run them up.”

The source added: “She’s not coming in the election with a divided state the way former Sen. Jesse Helms [R] was.”

And proof of Democratic skittishness appears to be in the pudding. Although still more than one year to Election Day, state Sen. Kay Hagan (D) and state Rep. Grier Martin (D), who served in Afghanistan, are the anticipated Democratic frontrunners, should they decide to run. While both are considered strong possibilities, they don’t hold statewide office and some Democrats worry that Dole’s wide name recognition could require millions of dollars in large-market television advertising.

DSCC spokesman Matthew Miller said the committee continues to stand by the earlier polls, claiming that “the overwhelming evidence is that her approval rating is in the 40s.” And while recruiting Democrats in Dixie is more difficult than in, say, New York or Pennsylvania, last year’s surprise victory by now-Sen. Jim Webb (D-Va.) may embolden others to test Southern GOP Senate seats once considered unattainable.

Jerry Meek, chairman of the North Carolina Democratic Party, also said that last year’s Democratic watershed has complicated recruiting efforts for next year’s Senate race. Regardless of the polling, he said it’s tough to convince Miller and other North Carolina House Members to walk away from their new majority, which few expect will disappear next cycle.

Meek, who said at least one credible Democratic challenger would emerge by November, also said fundraising was a concern for would-be candidates.

On Monday, Dole’s campaign said it expects to spend $20 million or more, a figure her campaign believes an eventual Democratic challenger will need to match — and a total that would outpace all but three 2006 Senate races.

“Part of it is also the fact that it’s going to be a very expensive race,” Meek said. “Even the people who have decided not to run are convinced that she’s vulnerable and can be beaten” if a challenger is adequately funded.

Meek and other Democrats also point to a factor polls may be ill-equipped to measure: like Virginia last year, a much-whispered-about migration surge by white-collar, once-GOP voters to suburban areas around the state.

North Carolina’s largest county, Mecklenberg, which takes in all of Charlotte, has experienced 15 percent population growth since 1990, according the North Carolina Office of State Budget and Management. According to the Bureau of Labor Statistics, last year the state’s rate of economic growth was 14th in the country, tied with California and Florida and ahead of New York, Illinois and fast- growing Nevada.

Last year, bad polling led the Democratic Congressional Campaign Committee to believe Rep. Robin Hayes’ (R-N.C.) Charlotte-area district was out of play. High school social studies teacher Larry Kissell (D) ended up losing to Hayes by 329 votes.

“We’re about to become the ninth-largest state in the country and it’s largely because of people who are moving to the state from other states,” Meek said. “Back home they might have voted Republican, but in North Carolina they realize the North Carolina Republican Party is not in step with their values.”