With his shirt sleeves rolled up and his suit jacket off, Obama delivered a campaign-style speech to a gymnasium of young people in Michigan in an effort to rev up his base for critical congressional elections, in which his party risks losing control of the U.S. Senate and seats in the House of Representatives.

The president is fresh off of a rare day of domestic policy success. On Tuesday, he announced 7.1 million people had signed up for coverage under Obamacare, his signature healthcare law, which has dogged him for months because of a disastrous rollout and a glitchy website.

Obama, who was to headline a pair of fund-raising events in Chicago later on Wednesday, took note of the healthcare enrollment number. But he spent most of his time focusing on his call to raise the national minimum wage to $10.10, a move Republicans oppose.

Obama said raising the minimum wage would raise millions of people out of poverty and many Republicans nationwide would like to make a raise happen, he said.

"Republicans in Congress don't want to vote to raise it at all. In fact some want to scrap the minimum wage," he said.

The crowd booed.

"No, no, don't boo, organize," he told them. "They may not hear the boos, but they can read a petition and they can see votes."

Obama needs the votes in November to help push back Republicans who see an opportunity for building on their majority in the House of Representatives and taking control of the U.S. Senate. A Republican-controlled Congress would make it far more difficult for Obama to gain approval of agenda items in his last two years in office.

One hope of the Democrats is Representative Gary Peters, who is running for a Senate seat in Michigan.

Although many Democrats have shied away from campaigning with Obama because of the unpopularity of the healthcare law, Peters joined the president on Wednesday. Obama bought him a sandwich at the popular local deli, Zingerman's.

"I'm happy to be with the president. I work with the president on issues that are important to middle-class families here in Michigan and families who aspire to be in the middle class," Peters told reporters. "I'm pleased to be with him and really pleased that he's focused on Michigan."

With a large blue banner declaring "Opportunity for all" and a big American flag, the gym had the feel of a the campaign venues Obama frequented as a candidate in 2008 and 2012.

His words had a similar ring as well. The president hammered Republicans for opposing his ideas and made clear that, despite its problems, he believes Obamacare is a winner for his party and a problem for the opposition.

"They do have one original idea, which is to repeal Obamacare," Obama said of Republicans. "Because they haven't tried that 50 times."

And he was sharply critical of a Republican proposal offered on Tuesday by Rep. Paul Ryan, chairman of the House Budget Committee, that would reduce government spending by $5 trillion over a decade.

Obama said the type of cuts required of the Ryan budget would be devastating to middle-class voters.

"If they were trying to sell this sandwich at Zingerman's, they'd have to call it the Stinkburger, or the Meanwich," he said.

(Additional reporting by Steve Holland and Mark Felsenthal in Washington. Editing by Andre Grenon)

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