On a politically focused trip aimed at revving up his base and raising cash, President Barack Obama on Wednesday urged supporters to help Democrats keep control of the U.S. Senate and declared this year to be his last campaign.

Buoyed by good news over his signature healthcare program, Obama touted proposals to raise the minimum wage and spur job creation that have little chance of passage in Congress during a rally with students in Michigan.

Later at a fundraiser in Chicago he underscored Democratic worries about their political vulnerabilities in the Senate and House of Representatives in November congressional elections.

"Even though I promised Michelle that 2012 was going to be my last campaign, actually this one's my last campaign," Obama, referring to his wife, told a fundraiser at the private home of longtime donors in his hometown of Chicago.

"We need to hold on to the Senate. We need to pick up seats in the House," he said. Obama was re-elected in 2012.

Obama's tone at the fundraiser was more subdued than the earlier rally-like event in Michigan, which occurred before a shooting at the Fort Hood Army base in Texas. In between fundraisers in Chicago, Obama told reporters he was "heartbroken" about the shooting and pledged to get to the bottom of what happened.

Before that, however, Obama spent the day in campaign mode.

In Ann Arbor, with his shirt sleeves rolled up and his suit jacket off, Obama noted 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.

Then he pressed his case for raising the national minimum wage to $10.10, a move Republicans oppose. Obama said the move would lift millions of people out of poverty.

"Republicans in Congress don't want to vote to raise it at all. In fact some want to scrap the minimum wage," he told the crowd of mostly young people, who proceeded to boo.

"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."

CAMPAIGN MODE

Obama needs the votes in November to help thwart Republicans, who see an opportunity to build on their majority in the House and take control of the Senate.

A Republican-controlled Congress would make it far more difficult for Obama to pass items from his agenda during 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 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 Representative 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.