PORTLAND — A recent survey of Maine voters shows that favorability ratings for President Barack Obama are lower in Maine than nationally, while Mitt Romney fares better in Maine than in the nation as a whole.

The spring 2012 tracking survey by Critical Insights, a Portland-based polling firm, shows that the president’s favorability ratings in Maine increased to 47 percent from 43 percent in the fall, when it hit the lowest level during his administration.

Obama’s national favorability rate is 56 percent, as measured a few weeks earlier in a separate survey.

Romney, the presumptive Republican presidential nominee, has a 51 percent favorability rating in Maine and a 35 percent rating nationally.

MaryEllen FitzGerald, president of Critical Insights, said the discrepancy between the state and national figures reflects Mainers’ tendency to be less exuberant and more likely to not offer an opinion.

“They tend to hold judgment a little closer,” she said. “They’re not as quick to say, ‘Yeah, I’m favorable.’ If they don’t know, they don’t’ know.”

FitzGerald said Mainers historically have higher numbers in the “don’t know” category.

For Obama, “don’t know” was 11 percent statewide and 5 percent nationally.

For Romney, 26 percent of Mainers polled didn’t say whether they have a favorable or unfavorable impression, or didn’t know. That compares with 18 percent nationally.

The survey has a margin of error of plus or minus 4 percentage points, which means it’s possible that Obama’s favorability rating in Maine may not have increased at all.

The survey, conducted from May 2-7, involved 600 telephone interviews of randomly selected residents who described themselves as registered voters. The national figures are from an ABC News/Washington Post conducted April 11-15.

Brian Duff, a political scientist at the University of New England, said Romney’s high rating could be interpreted as lukewarm favorability based on his status as governor of neighboring Massachusetts and the lack of primary advertising targeting Romney in the state.

“The more people learn about Romney, the less they like him,” Duff said. “People who voted for him often voted for him because they hated Gingrich or Santorum.”

Duff noted that some poll figures — including Mainers’ view of how Obama is handling gas prices — were not great for the president. Only three of 10 Mainers said they approve of how he is handling the situation, a figure in line with national sentiment.

“If you were Obama’s guy in Maine, it’s a little sobering, but I wouldn’t be panicking,” he said.

Ronald Schmidt Jr., a political scientist at the University of Southern Maine, said it’s useful to think of polls as snapshots of particular moments, and to remember that there are many moments yet to be captured before the election.

“This far out, when the general election is so far out, I wouldn’t make too much of the data,” he said.