The former president’s speech will be a high point in a checkered relationship between two men who sparred, sometimes sharply, in the 2008 primaries, when Clinton was supporting wife Hillary’s campaign for the nomination.

If Day 2 of the Democrats’ convention was all about grabbing some of Clinton’s luster, opening day was designed to portray Obama as someone who understands the problems of ordinary people.

Michelle Obama played those cards with force in a speech declaring that after four years as president, her husband is still the man who drove a rust-bucket on early dates, rescued a coffee table from the trash and knows the struggles of everyday Americans because he lived them in full.

“I have seen firsthand that being president doesn’t change who you are, it reveals who you are,” the first lady said to lusty cheers Tuesday night in a deeply personal, yet unmistakably political testimonial.

Obama, who watched his wife’s address back in Washington, arrives in the convention city Wednesday afternoon to prepare for his own convention-closing speech Thursday in the 74,000-seat Bank of America stadium — if uncertain weather permits the outdoor venue.

Rahm Emanuel, the Chicago mayor who served under both Clinton and Obama, made the rounds of morning talk shows Wednesday to trace a connection between the two presidents’ “similar values, similar policies and similar objectives.”

“He can do nothing but help,” Emanuel said, rejecting any notion that Clinton’s ability to get things done and work with Republicans would somehow diminish perceptions of Obama.

But former New Hampshire Gov. John Sununu, writing in the New Hampshire Union Leader, said Clinton’s speech “will serve to remind the world of a time when the leadership of the Democratic Party took fiscal responsibility seriously. It might even induce nostalgia for the days of balanced budgets and bipartisan accomplishments such as welfare reform.”

While Bill Clinton reclaims the political spotlight, his wife will be worlds away — in distance and substance. Obama’s secretary of state is midway through an 11-day, six-nation tour of the Asia-Pacific region that started in the Cook Islands and ends in Russia. She should be in East Timor by the time her husband speaks.

Republican presidential candidate Mitt Romney, the career venture capitalist, appeared nowhere in Mrs. Obama’s remarks. But there was no mistaking the contrast she was drawing when she laid out certain values, “that how hard you work matters more than how much you make, that helping others means more than just getting ahead yourself.”

Such subtleties were otherwise missing from the stage as speaker after speaker teed up to take a strip off Romney and the Republicans, answering the catcalls of last week’s GOP convention in kind. The party’s up-and-coming Julian Castro, mayor of San Antonio, Texas, captured the tone in branding Romney a millionaire “who doesn’t get it.” Said former Ohio Gov. Ted Strickland, “If Mitt was Santa Claus, he’d fire the reindeer and outsource the elves.”

Polling gives Obama a consistent advantage over Romney as the more empathetic and in-touch leader. But the sputtering economy is the topmost voter concern and Obama’s highest mountain to climb after more than 42 months of unemployment surpassing 8 percent, the longest such stretch since the end of World War II. No president since the Great Depression has been re-elected with joblessness so high.

Romney had no public schedule during the Democrats’ convention. But running mate Paul Ryan kept up his criticisms of the Democrats, saying the convention’s first day was “what you expect when you have a president who cannot run on his record.”

“What you did not hear is that people are better off than they were four years ago,” he said on Fox News.

The GOP released a new web video showcasing the story of a man who lost his job and got back on his feet through the welfare-to-work requirements enacted under Clinton. Republican Chairman Reince Priebus said Obama was gutting the work requirements, “holding back the prosperity of so many who are scraping to get by.”

Obama adviser Valerie Jarrett, making the case for Obama’s economic policies in an appearance on MSNBC, said the president has a strong argument to make that people are doing better, but she acknowledged that “Americans are sitting around the breakfast table trying to figure out to make ends meet, so we have work to do.”

A new report found manufacturing activity declined for a third straight month. The Treasury Department announced Tuesday that the government’s debt passed $16 trillion. And the latest unemployment report, coming Friday, offers more potential fodder for Romney’s case against his rival’s stewardship unless it shows marked improvement. The GOP candidate took a few days’ hiatus from the campaign trail, preparing in Vermont for three fall debates with Obama that could prove pivotal in this close election.

Recalling life before Washington, Mrs. Obama spoke of the “guy who’d picked me up for our dates in a car that was so rusted out, I could actually see the pavement going by through a hole in the passenger-side door.” She described a marriage of kindred spirits, both from humble roots, and said the president’s work on health care, college loans and more all come from that experience. “These issues aren’t political” for him, she said. “They’re personal.”

“Barack knows what it means when a family struggles,” she said. “He knows what it means to want something more for your kids and grandkids.”

The first lady took the stage as the most popular figure in this year’s presidential campaign. Michelle Obama earns higher favorability ratings than her husband, Romney, his wife, Ann, or either candidate for the vice presidency, according to the latest Associated Press-GfK poll. And views of Mrs. Obama tilt favorably among independents and women, two focal points in her husband’s campaign for re-election.

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By Calvin Woodward and Julie Pace. Woodward reported from Washington. Associated Press writers Jennifer Agiesta and Jack Gillum in Washington, Matthew Daly in Norfolk, Va., Steve Peoples in Ohio, Kasie Hunt in Vermont, , Thomas Beaumont in Des Moines, Iowa, and Ken Thomas, Matt Michaels and Jim Kuhnhenn in Charlotte contributed.