Facing a public still wary of his massive health care overhaul, President Barack Obama urged Americans not to judge the nearly $1 trillion legislation he signed into law last week until the reforms take hold.

During an enthusiastic, campaign-style appearance in Maine's largest city, Obama mocked the pundits and pollsters who say he isn't getting a boost from his yearlong campaign to pass the sweeping reform.

"Every day since I signed reform into law, there's another poll or headline that says, 'Nation still divided on health reform, no great surge in public support,'" Obama said in prepared remarks. "It's been a week, folks. So before we find out if people like health care reform, we should wait to see what happens when we actually put it into place. Just a thought."

The president's overhaul extends health coverage to 32 million people who are uninsured and will shape how almost every American receives and pays for medical treatment. Some aspects of the plan go into effect this year, but president himself has said it could take four years for the full overhaul to take hold.

Obama's trip to Portland took him to the home state of two moderate Republican senators, Susan Collins and Olympia Snowe, whose votes for the legislation the president ardently sought but ultimately could not win. The White House said both senators were invited to attend the event, but neither did.

During the speech, one in a series of appearances to sell the health reforms, Obama focused on his health plan's short- and long-term impact on small businesses, many of which have suffered during the economic downturn.

Under the plan, businesses that have 25 or fewer employees with average annual wages of less than $50,000 will receive tax credits this year if they provide health care coverage to their workers. Those credits are expected to increase by 2014, with 4 million small businesses benefiting, according to the White House.

"This health care tax is pro-jobs, it's pro-business and it starts this year," Obama said.

Also starting in 2014, companies with up to 100 employees will be able to buy insurance through new state-based purchasing pools, or exchanges, with the goal of giving small businesses the same kind of purchasing power as larger companies. About 22 million self-employed Americans will also be able to purchase insurance through the exchanges.

Congressional Republicans were united against the law and many predict that Democrats who voted for it will be dragged down in the November elections. Some Republicans are calling for repeal, and Obama told opponents of the bill to "go for it."

"If these congressmen in Washington want to come here to Maine and tell small business owners that they plan to take away their tax credits and essentially raise their taxes, be my guest," he said.

After speaking in Maine, Obama planned to travel to Boston to attend two fundraisers for the Democratic National Committee. His trip comes as much of the Northeast is suffering through devastating flooding caused by record-setting rainfall.

One of Rhode Island's Democratic congressmen, Rep. Jim Langevin, sent a letter to the White House on Thursday requesting that Obama view the damage to that state during his travels. Homeland Security Secretary Janet Napolitano plans to travel to Rhode Island on Friday.

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Associated Press writers David Sharp and Karen Testa contributed to this report.