Portland, Maine (Reuters) - President Barack Obama focused on immediate benefits for small businesses in his healthcare overhaul on Thursday as he made his second speech this week promoting the sweeping plan to a skeptical public.

Opinion polls signal that many voters are unhappy with the healthcare overhaul amid high unemployment and a still-sluggish economy, and could punish Obama's Democratic Party in mid-term congressional elections in November.

In his speech, Obama reiterated his message that the plan is part of his program to boost the economy and employment.

"I want you to know that we are working every day to spur job creation and turn this economy around," he said in prepared remarks. "And that's why we worked so hard over the last year to lift one of the biggest burdens facing middle-class families and small business owners: the crushing cost of health care in America."

The 35 percent tax credit for small businesses, available from the start of 2010, is part of a $940 billion package of changes to the country's $2.5 trillion healthcare industry that represents the largest U.S. social policy shake-up in decades.

Democrats, who currently control both the House of Representatives and the U.S.

Senate, passed the healthcare legislation without a single Republican vote.

Republicans hope they can turn the issue into a vote-winner, with polls showing a majority of the country fearing the reform will cost to much and invites unwelcome government intrusion into their lives.

Obama urged Americans to see what benefits they experience from the new law -- a vital achievement for his presidency -- before they judge it, but acknowledged that it is not perfect.

"This reform will not solve every problem with our healthcare system. It will not bring down the cost of healthcare overnight," he said. "We'll have to make some adjustments along the way."

He aimed squarely at insurance companies and rival Republicans in his remarks, praising healthcare's passage as a victory over special interests and misinformation.

"There has been plenty of fear-mongering and overheated rhetoric," he said. "And if you turn on the news, you'll see that those same folks are still shouting about how the world will end because we passed this bill. This is not an exaggeration. Leaders of the Republican Party have actually been calling the passage of this bill 'Armageddon.'"

(Additional reporting by Patricia Zengerle, editing by Alan Elsner)