Watch John King's interview with DeMint on "John King, USA" at 7 p.m. ET on CNN.
(CNN) -- President Barack Obama told a Labor Day crowd in Detroit that he's prepared to fight for a new job growth plan, defend organized labor and take steps to "restore the middle class in America," while five Republican candidates hoping to defeat him next year all called for repealing the major legislation passed so far in Obama's presidency.
The Republican presidential candidates participating in the Palmetto Freedom Forum in Columbia, South Carolina, which was televised on CNN, were unified in advocating the end of the health care reform law and the Wall Street reform measure passed by a Democratic-led Congress.
They also all expressed strong anti-abortion views and their belief in marriage being between a man and a woman at the event set up by Sen. Jim DeMint, a leading tea party conservative.
Meanwhile, in the early primary states of New Hampshire and South Carolina, other Republican presidential contenders ripped Obama's handling of the economy and pledged to take an economically battered America in a new direction marked by less spending and fewer regulations.
The sharply differing visions raised new questions about the ability of top Democrats and Republicans to tackle pressing budgetary and other issues while positioning themselves for what promises to be a bitterly contested campaign next year.
In a speech that likely previewed his scheduled address Thursday to a joint session of Congress to present a jobs plan, Obama directly challenged Republicans, whom he has accused of obstructing progress in order to score political points.
"These are tough times for working Americans," Obama told the union-dominated crowd at a rally that included a warm-up from Aretha Franklin. "The time for Washington games is over. The time for action is now."
Saying American workers were ready to move ahead, he said, "We just need Congress to get on board" and later added: "We will see if congressional members will put country before party."
"We will give them a plan and then we will see if they want to create jobs," the president said.
Obama took credit for a series of controversial measures, including the health care overhaul, financial regulatory reform, the 2009 economic stimulus plan and the auto industry bailout.
"I've seen Detroit prove the cynics and the naysayers wrong," he said, referring to the U.S. auto industry. "We're fighting for good jobs with good wages ... (and) an economy where hard work pays off and gaming the system doesn't work."
The president quoted a 1948 Labor Day speech delivered by President Harry Truman in Detroit. Like Obama, Truman ran for re-election that year against a largely hostile Republican-dominated Congress.
"The gains of labor were not accomplished at the expense of the rest of the nation," Obama said, quoting Truman. "Labor's gains contributed to the rest of the nation's prosperity."
Before Obama spoke, James Hoffa, president of the International Brotherhood of Teamsters, blasted congressional Republicans and urged the crowd to mobilize and help defeat the GOP at the polls in 2012.
"Everybody here has a vote," Hoffa said. "Keep the eye on the prize. Let's take these sons of bitches out and give America back to an America where we belong."
As Obama rallied Democratic base voters in Michigan, Vice President Joe Biden headed to Cincinnati to attend an AFL-CIO Labor Day event. The AFL-CIO is a federation of 56 national and international labor unions.
Obama carried Michigan and Ohio in 2008, but both states, hit hard by the economic downturn, could prove challenging to keep in the Democratic column in 2012.
The Republican forum in DeMint's home state of South Carolina, meanwhile, gave five of the top GOP candidates a chance to explain their stances on key issues to conservatives.
DeMint's endorsement is one of the most sought after among 2012 GOP White House hopefuls, and his support would be a major boost for any Republican candidate in his home state's pivotal early primary.
Former Massachusetts Gov. Mitt Romney initially declined DeMint's invitation, saying he was concentrating on campaigning in New Hampshire, which holds an even earlier primary. But after falling behind newcomer Texas Gov. Rick Perry in some polls, Romney apparently changed his mind, opting to wrap up a pancake breakfast event in New Hampshire before traveling to Columbia for DeMint's forum.
"The tea party is a powerful movement saying government's too big, and I couldn't agree more," Romney told a crowd of roughly 450 people at the breakfast.
In addition to Romney, Rep. Michele Bachmann of Minnesota, businessman Herman Cain, former House Speaker Newt Gingrich and Rep. Ron Paul of Texas attended the DeMint forum.
All cited the Declaration of Independence and its determination of God-given rights for citizens as the foundation of American government in a recitation of core conservative principles championed by the tea party movement.
Perry was also slated to take part in DeMint's forum but backed out Monday morning to return to Texas as it battles growing wildfires.
Perry did, however, participate in GOP Rep. Tim Scott's town hall series in Conway, South Carolina, before returning home.
While in Conway, Perry sharply criticized Romney's job growth record in Massachusetts.
"There's one (GOP candidate) ... that's created jobs all over the world," Perry said, referring to Romney's oft-mentioned record in the private sector. "But while he was the governor of Massachusetts, he didn't create very many jobs.
"We cannot choose a nominee ... that is going to blur the lines," Perry added. The GOP needs "someone who has a very stark difference (with) the president of the United States ... and I would suggest to you I'm that person."
Two other candidates not appearing at the event were also on the campaign trail Monday. Former Utah Gov. Jon Huntsman, drawing new attention after announcing his economic plan last week, wrapped up five days of events in New Hampshire with a parade and a picnic, and former Sen. Rick Santorum of Pennsylvania held three events in South Carolina.
Former Alaska Gov. Sarah Palin, who has not announced whether she will run for president, was in New Hampshire on Labor Day after three days in Iowa.
"We're up against ... Barack Obama's very strange fundamental transformation of the country that we so love," Palin said. "We don't need a transformation. As you know, we need a fundamental restoration of all that is good and strong and free in America."
CNN's Alan Silverleib, Shawna Shepherd, Tom Cohen and Paul Steinhauser contributed to this report.