PORTLAND – A statewide poll released Thursday as President Bush rallied supporters at Bangor International Airport had the Republican incumbent locked in a close race with Democrat John Kerry.

The poll by Critical Insights put Kerry at 45 percent and Bush at 42 percent among likely voters, while 10 percent remained undecided. Independent Ralph Nader trailed with 3 percent among likely voters.

“It seems to me that this poll does indicate what we’re seeing in a lot of battleground states: It’s a close race,” said Tony Corrado, a Colby College professor who is working at the Brookings Institution.

The poll showed Bush gained 3 points and Kerry dropped 5 points since the last Critical Insights poll in the spring.

Then, Bush was at the depth of dissatisfaction among voters as he struggled with less cheerful economic news, the war in Iraq and the emerging Abu Ghraib prison scandal, Corrado noted.

The new poll by Critical Insights was based on telephone surveys of 600 people across Maine from Sept. 10 to Sept. 23. When broken down by likely voters, the margin of error was 4.5 percentage points.

“Likely voters” had to meet the following criteria: They had to be registered to vote, know their polling place, cast tallies in the last election and indicate they were “highly likely” to vote on Nov. 2.

President MaryEllen FitzGerald said 90 percent of the respondents met all of the criteria as “likely voters” because of Maine’s tradition of high turnout in presidential elections along with two referendums that have inspired passion across the state: bear baiting and the tax cap.

Those referendums could shake things up by luring to the polls people who otherwise might not vote, she said.

The poll’s findings suggested national security issues trump domestic issues among many likely voters in Maine.

Kerry led when respondents were asked about health care, education, jobs and the economy. But Kerry and Bush were even on foreign policy and what to do in Iraq, and Bush had a 15-point lead when voters were asked who was better suited to defend the country against future terrorist attacks.

Even though he was perceived in the poll as weaker than Bush on terrorism, Kerry is strong on domestic issues that matter to Maine, Corrado said.

“It’s not surprising to find that Kerry has a slight lead given the economic challenges that Maine has faced over the last four years and the enduring problems of health care in the state,” Corrado said.