A new poll puts former Maryland governor Bob Ehrlich in a statistical dead heat with Democratic Gov. Martin O'Malley, driven by a growing disaffection among Democrats.

Ehrlich, a Republican, won 47 percent of votes compared with O'Malley's 46 percent in a Rasmussen telephone survey of 500 likely Maryland voters. Five percent said they were undecided, while 2 percent said they prefer another candidate. A 4.5 percent margin of error puts the candidates tied.

"Voters are restless and are concerned about the state of the Maryland economy," said John White, a politics professor at Catholic University. The small percentage of undecided voters so early in the campaign indicates party lines are drawn in most districts, and the election is alreadyhinging on one or two key counties.

The candidates have made clear that county is Montgomery.

"Montgomery has become the engine that drives Maryland politics," White said, noting it is home to the state's largest percentage of independents.

O'Malley won 62 percent of votes in the strongly Democratic county in 2006, compared with Ehrlich's 37 percent.

"If he could bump up three or four points [in Montgomery], Ehrlich could win this election," said Jerry Pasternak, who served 12 years as senior political and policy adviser to former Montgomery County Executive Doug Duncan. "O'Malley must contain those numbers to below the 39 or 40 percent number to win."

Former Montgomery County Councilwoman Nancy Dacek said the county's voters are turning away from O'Malley because they are fed up with high taxes and a stagnant economy.

"I think Montgomery County voters -- and particularly older voters -- are tired of seeing their money fly out the window," said Dacek, a Republican. "I know so many people that move to Florida once they're retired because it's very, very expensive to live in this county and continue to serve as the piggy bank of the state forever."

She criticized the county's income and energy taxes, and said the local and state governments keep turning to Montgomery's well-to-do taxpayers to control ballooning deficits.

Polling trends also show Ehrlich is taking Democrats from O'Malley.

Twenty-two percent of Democrats said they would vote for Ehrlich, as opposed to O'Malley's 8 percent of Republicans -- a finding supported by a Magellan Data and Mapping Strategies poll last week.

"We always knew that this would be a tough election," said O'Malley campaign manager Rick Abbruzzese, touting O'Malley's success at reducing violent crime to historic lows and maintaining record levels of spending on education. "We must remember polls are only snapshots in time," he said.

Democrats, who control the governor's office and state legislature, are taking the brunt of Marylanders' frustrations over the state's economic troubles -- which included a $2 billion budget gap for fiscal 2011, Pasternak said.

"The question is, are those independent voters and those dissatisfied Democrats angry enough to turn out and vote for a Republican?"