Sen. Barack Obama and Sen. Susan Collins hold double-digit leads over their opponents in the presidential and U.S. Senate races in Maine, according to a new poll released Wednesday by the U.S. Chamber of Commerce.

Obama, the presumptive Democratic presidential nominee, leads Sen. John McCain, the presumptive GOP nominee, by 12 points while Collins, a Republican, leads Democratic Rep. Tom Allen by 14 points.

In the presidential race, Obama leads McCain 49 to 37 percent and 11 percent are undecided. Collins leads Allen 55 to 41 percent.

Obama leads among voters under age 35, among women and he is running even with McCain among male voters.

McCain leads among older voters.

Obama leads 54 to 29 percent among independent voters, who outnumber registered Democrats and registered Republicans.

Obama and McCain are nearly tied among small business owners and self-described supporters of the business community.

The poll also sampled voters in the Portland media market and the Bangor – Presque Isle market. Obama led 50 to 36 percent in the southern part of the state and 49 to 38 percent in the northern part of the state.

See more below about the U.S. Senate race.

Democratic Rep. Tom Allen and Republican Sen. Susan Collins will face a third opponent in the Nov. 4 general election: Herbert Hoffman, an independent anti-war, pro-impeachment candidate.

Secretary of State Matt Dunlap on Monday rejected the Maine Democratic Party’s challenge to keep Hoffman off of the ballot. The party alleged that Hoffman’s petitions were invalid because he was not in the area where registered voters were signing them.

“I’m very gratified that the Secretary of State has upheld the hearing officer’s recommendation. This is a vindication of my petition efforts and it is also a ruling in favor of voters’ rights,” Hoffman said in a phone interview.

The ruling ends a two-week long dispute between Hoffman and the Maine Democratic Party, which began earlier this month when Hoffman submitted 4,112 signature to qualify for the ballot. He needed 4,000.

But the Maine Democratic Party challenged the validity of some of the signatures.

The two parties met at a hearing before the Secretary of State’s office on Monday. After reviewing the party’s complaints, Julie Flynn, Maine’s Deputy Secretary of State, found that 74 signatures were invalid, leaving Hoffman with 4,038 signatures.

“There’s no pattern of forethought of abuse,” Dunlap said, adding that the state party’s challenge “was not sufficient” to keep Hoffman off of the ballot.

Below is the statement from the Maine Democratic Party.

Sen. John McCain, the presumptive Republican presidential nominee, will attend a fundraiser at the home of former President George Bush in Kennebunkport on July 31, according to an invitation that has been sent out.

(UPDATE: The campaign says that this date is tentative and subject to change).

There is a photo-op with Bush and his wife, Barbara, at 11:30 and a small reception at 12 (that's for the high dollar donors). There's a bigger reception at The Colony Hotel on Ocean Avenue at 12:30.

Unless McCain or Sen. Barack Obama get to Maine before then, that will mark the first visit by a presidential candidate to the state. It's unclear now if McCain will hold a campaign rally.