CHARLOTTE, North Carolina (CNN) - A Democratic National Convention vital to President Barack Obama's re-election bid will hear from former President Bill Clinton on Wednesday after the first lady and other opening night speakers urged supporters to fight for a man they portrayed as a strong leader committed to equal opportunity for all.
The second day of the convention began with bad news for organizers, who decided to move Obama's concluding speech on Thursday night -- the highlight of the three-day political conclave -- because of predicted severe weather in the Charlotte area.
Instead of speaking at the 73,000-capacity Bank of America outdoor stadium, the president will address about 20,000 in the Times Warner Cable Arena, where the rest of the convention is taking place.
Obama campaign officials said they were "disappointed" at having to make the decision, but called it a public safety issue. They are encouraging those scheduled to attend at the stadium to instead organize block parties in their neighborhoods.
Despite the change, campaign officials were enthusiastic about the start of the convention on Tuesday, with one senior official calling the program that featured powerful and at times emotional speeches by first lady Michelle Obama and others a "fantastic, high energy night."
CNN Senior Political Analyst David Gergen agreed that the opening night couldn't have gone much better, adding: "If they have two more nights like this, they could possibly break this race open."
Cheering delegates also heard plentiful criticism of Republican challenger Mitt Romney as Democrats launched their response to last week's GOP convention, which sought to frame the November election as a referendum on Obama's presidency amid high unemployment, sluggish economic growth, and mounting federal deficits and debt.
Facing a tight race and Republican attacks that Obama has made things worse while in office, Democratic organizers planned a convention that emphasizes the tough decisions the president has made so far and the additional steps needed to bolster the middle class.
Clinton will continue those themes on Wednesday, drawing parallels between his policies in the 1990s and the proposals by Obama today that are intended to bring the results similar to the budget surplus and economic growth of the Clinton presidency, senior convention officials told CNN on Wednesday.
The policies Clinton was advocating with his "Bridge to the 21st Century" theme at the 1996 Democratic convention "really do add up to the balanced approach President Obama is calling for," one of the senior convention officials said, citing proposals such as government spending on education, infrastructure development and innovation. "There are some dramatic echoes between the two presidents."
Other speakers Wednesday will include Elizabeth Warren, the consumer protection advocate behind the Wall Street reform bill passed under Obama who now is running for the U.S. Senate seat in Massachusetts against incumbent Republican Scott Brown, and former business associates of Romney during his years running the private equity firm Bain Capital.
On Tuesday, speech after speech lambasted Romney and Republicans, accusing them of being out of touch and politically divisive at a time requiring national unity. Seeking to further strengthen Obama's advantage with women, Hispanic Americans and young voters, the Democratic speakers hailed the president for promoting health care reforms, supporting gay marriage and ending deportations of some young illegal immigrants.
Michelle Obama offered a personal perspective on why her husband should be re-elected, telling the convention that the same values she fell in love with guide him each day in the White House.
"In the end, for Barack, these issues aren't political, they're personal," she said. "Barack knows the American Dream because he's lived it, and he wants everyone, everyone in this country to have the same opportunity, no matter who we are, or where we're from, or what we look like, or who we love."
Massachusetts Gov. Deval Patrick earlier challenged Obama supporters to be more forceful in supporting the president's record in the face of unrelenting Republican attempts to discredit the administration's accomplishments, such as ending the Iraq war and delivering "the security of health care to every single American in every single corner of the country."
"It's time for Democrats to grow a backbone and stand up for what we believe," he said to prolonged cheers.
Health and Human Services Secretary Kathleen Sebelius defended the 2010 health care law despised by Republicans, saying the provisions that prevent insurance companies from denying coverage for pre-existing conditions and allow parents to keep their children on family policies up to age 26 are "what change looks like."
San Antonio Mayor Julian Castro in his keynote address declared, "Mitt Romney, quite simply, doesn't get it," later adding: "We know that in our free-market economy, some will prosper more than others. What we don't accept is the idea that some folks won't even get a chance."
Romney and Republicans "are perfectly comfortable with that America. In fact, that's exactly what they're promising us," Castro said.
Other speakers mocked Romney's overseas financial holdings -- a Swiss bank account, a Cayman Islands tax shelter -- revealed in the two years of tax returns the former Massachusetts governor has released so far. Senate Majority Leader Harry Reid challenged Romney to make public more of his tax records, citing the example of the 12 years of returns Romney's father, George, made public in his 1968 presidential run.
"Trust comes from transparency, and Mitt Romney comes up short on both," Reid said.
In a video message to the convention, former President Jimmy Carter said Obama prioritized the middle class in making the difficult decisions required of the nation's highest office.
"He has done it all in the face of bitter, unyielding, in fact unprecedented partisan opposition," Carter said in reference to congressional Republicans.
Later, Chicago Mayor Rahm Emanuel recalled the litany of crises that greeted the Obama administration when it assumed office in January 2009: a Wall Street meltdown, economic recession, wars in Iraq and Afghanistan, a collapsing auto industry.
"Each crisis was so deep, and so dangerous, any one of them would have defined another presidency," said Emanuel, who was Obama's chief of staff at the time. "We faced a once-in-a-generation moment in American history, and fortunately, we have a once-in-a-generation president."
Other speakers told how Obama's decision to bail out the struggling auto industry saved vital jobs and kept a mainstay of the U.S. economy afloat. The goal was to contrast a politically unpopular decision -- spending tax dollars to help a private industry -- with Romney's call at the time to let Detroit go bankrupt. Romney now says he advocated a managed bankruptcy similar to the eventual result under Obama.
The Romney campaign said no amount of rhetoric could mask what spokeswoman Andrea Saul called Obama's "record of disappointment and failure."
"On the first night of President Obama's convention, not a single speaker uttered the words 'Americans are better off than they were four years ago,'" Saul said in a statement, adding that "the American people will hold President Obama accountable for his record."
Senior campaign officials told CNN that the convention has three main objectives: to outline the clear choice facing voters, to highlight Obama's leadership in championing necessary but politically unpopular steps such as health care reform and the auto bailout, and to present a detailed plan for creating jobs for the middle class.
Romney's campaign is focused on the question of whether Obama has made life better for Americans, arguing that continued economic woes show that White House policies have failed to deliver a recovery from the recession that began during the previous Republican administration.
The "are you better off" strategy was famously employed in 1980 by Ronald Reagan, who asked voters that question when running against the incumbent Carter at a time of national economic woes. Reagan went on to win, and the Romney campaign has repeatedly invoked his name this year while seeking to link Obama and Carter as failed leaders
The Romney campaign continued that strategy Wednesday with an appearance by vice presidential nominee Rep .Paul Ryan in Iowa.
"We are going to hear a lot of things in Charlotte, but we are not going to hear a convincing argument that we are better off than we were four years ago," he told supporters in Adel.
Ryan, the conservative House Budget Committee chairman from Wisconsin, also sought to undermine Clinton's speech, saying, "My guess is we'll get a great rendition of how good things were in the 1990s, but we are not going to hear much about how things have been in the last four years."
The back-and-forth between the campaigns is part of their struggle to define the election in the minds of voters. Republicans want it to be about Obama's presidency, while Democrats seek a choice between differing political ideologies on the size and role of government.
In particular, Republicans seek to shrink the size of government and end chronic federal deficits and rising national debt through reducing spending, reforming entitlement programs such as Social Security, Medicare and Medicaid, and slashing taxes on businesses and many individuals as a spur for economic growth.
Obama and Democrats argue that a deficit reduction plan also needs additional revenue, and they propose allowing tax rates on income of more than $250,000 for families and $200,000 for individuals to return to the higher levels of the 1990s.
Republicans oppose any kind of tax increase, and the impasse over that issue has been the main impediment to a comprehensive deficit reduction agreement during Obama's first term.
The race overall is very tight, with a new poll Tuesday showing Romney received little bounce from last week's convention intended to introduce him to voters just now turning their attention to the presidential race.
The CNN/ORC International survey also indicates that less than 40% of registered voters said the GOP convention made them more likely to vote for Romney. At the same time, Romney got a slight bump in his favorable rating, and on being in touch with the middle class and women, although he still trails Obama on those two questions.
CNN's previous poll, released as the Republican convention got under way, indicated that 49% of likely voters backed Obama, with 47% supporting Romney, a statistical tie. In the new survey, which was conducted after the GOP convention, both the president and Romney are at 48%.
"The Republican convention had at best a mild effect on the presidential race, and from a statistical viewpoint, no effect at all," said CNN Polling Director Keating Holland.
CNN's Ashley Killough, Kevin Liptak, Sarah Aarthun, Halimah Abdullah, Paul Steinhauser, Adam Aigner-Treworgy and Peter Hamby contributed to this report.