PORTLAND – A new poll suggests a 19-point lead for Barack Obama over John McCain in the presidential race in Maine, while Republican Sen. Susan Collins maintains a 17-point lead over her Democratic challenger, Rep. Tom Allen.

The poll released Tuesday by Market Decisions also indicates a referendum calling for a casino to be built in Oxford County is too close to call.

With a week left before Election Day, the poll found that 52 percent of those surveyed were either for Obama or leaning toward Obama with 33 percent for McCain. Fifty-four percent were for Collins or leaning toward her, compared to 37 percent for Allen. On the casino question, 49 percent supported a casino and 48 percent were opposed.

The poll indicated 87 percent of likely voters were dissatisfied with the way things are going in the U.S., said Curtis Mildner, president of Market Decisions.

A year ago, the presidential election was expected to be a referendum on the war in Iraq, but has since turned into a referendum on the economy, Mildner said. Either way, Obama’s message of change has caught on with voters, he said.

“A year ago it was the war in Iraq people wanted to change. Now it’s the economy people want to change,” Mildner said. “The fact that so many people are dissatisfied says ‘regime change,’ regardless of the issue.”

Market Decisions, a Portland-based research firm, conducted the telephone survey of 425 people between Oct. 13 and 26. It has a margin of error of plus or minus 5 percentage points.

In the Senate race, the poll found that Collins leads Allen among those who are dissatisfied with the way things are going. Of the likely voters who said they were dissatisfied, 50 percent were for Collins and 40 percent for Allen.

The poll results suggest a tight race on the casino referendum. Less than 4 percent of those surveyed were undecided.

Mildner said voters apparently are being influenced by the large amount of advertising in support of a casino. Olympia Gaming of Las Vegas is proposing to build a $184 million resort casino in Oxford that would have slot machines and table games. The company says the casino would have 800 employees.

The poll also showed strong support for a referendum question that would do away with a newly passed tax on beer, wine, soda and other beverages that would help fund the state’s Dirigo Health program.

Sixty-six percent of those polled said they favored repealing the tax with 28 percent against a repeal.

Mildner said repeal supporters have run an effective grass-roots campaign with posters and campaign signs at convenience stores, bars and restaurants.

“I think the difference in the campaign has been the level of advertising in support of the referendum,” he said. “It’s everywhere.”