Obama strode onstage as Clinton concluded his speech. The 42nd president bowed, and was pulled into an embrace by the 44th as thousands of delegates jammed into the convention hall roared their approval.
Clinton, conceding that many struggling in a slow-recovery economy don't yet feel improvement, said circumstances are indeed getting better, "and if you'll renew the president's contract you will feel it."
To more cheers, he said of Obama, "I want to nominate a man who is cool on the outside but who burns for America on the inside."
Not long afterward, the delegates formally awarded Obama their nomination to a second term in a post-midnight roll call of the states.
Clinton spoke as Obama's high command worked to control the political fallout from an embarrassing retreat on the party platform, just two months from Election Day in the tight race with Republican challenger Mitt Romney.
Under criticism from Romney, the Obama camp abruptly rewrote the day-old document to insert a reference to God and to declare that Jerusalem "is and will remain the capital of Israel." Some delegates objected loudly, but Los Angeles Mayor Antonio Villaraigosa, presiding in the largely-empty hall, ruled them outvoted. White House aides said Obama had personally ordered the changes, but they did not disclose whether he had approved the earlier version.
The convention concludes Thursday with Obama's acceptance speech before a prime- time national TV audience. Aides announced he would speak in the convention hall rather than a nearby 74,000-seat football stadium as originally planned. They cited weather concerns as the reason for the switch in a city that has been hit by heavy rains in recent days.
Romney, nominated at his own convention last week, spent his second straight day in Vermont preparing for next month's debates with Obama.
Clinton's speech was deemed so important by Obama's campaign aides that they delayed the president's formal nomination to a second term until it was over. The familiar roll call of the states began well after television prime time in the eastern part of the country, and the hall was emptying out rapidly as it dragged on past midnight.
Obama's campaign hoped the former president would prove especially persuasive in an era of sluggish economic growth and 8.3 percent unemployment. Clinton is exceptionally popular 12 years after he left office, particularly among white men, a group among whom Obama polls poorly.
The speech was vintage Clinton, overlong for sure, insults delivered with a folksy grin, references to his own time in office and his wife Hillary, all designed to improve Obama's shaky re-election prospects.
The convention hall rocked with delegates' applause and cheers the former president strode onstage to sounds of "Don't Stop Thinking About Tomorrow," his 1992 campaign theme song.
He sought to rebut every major criticism Republicans leveled against the president at their own convention last week in Tampa, and said that in fact, since 1961, far more jobs have been created under Democratic presidents than when Republicans sat in the White House, by a margin of 42 million to 24 million.
Clinton accused Republicans of proposing "the same old policies that got us into trouble in the first place" and led to a near financial meltdown. Those, he said, include efforts to provide "tax cuts for higher-income Americans, more money for defense than the Pentagon wants and ... deep cuts on programs that help the middle class and poor children."
"As another president once said, 'There they go again,'" he said, quoting Ronald Reagan, who often uttered the remark as a rebuke to Democrats.
There was another reference to Reagan, whom Democrats routinely accused of advocating "trickle down economics" that favored the rich.
" We simply cannot afford to turn the reins of government over to someone who will double down on trickle-down," Clinton said.
He shared prime time with Elizabeth Warren, the Democratic candidate for a Republican-held Senate seat in Romney's Massachusetts. For many years "our middle class has been chipped, squeezed and hammered," she said.
In a tight race for the White House and with control of the Senate at stake, Democrats signaled unmistakable concern about the growing financial disadvantage they confront. Officials said Chicago Mayor Rahm Emanuel, who was Obama's first White House chief of staff, was resigning as national co-chair of the president's campaign to help raise money for a super PAC that supports the his re-election.
Unlike candidates, outside groups can solicit donations of unlimited size from donors. At the same time, federal law bars coordination with the campaigns.
Inside the hall, a parade of speakers praised Obama and criticized the Republicans, sometimes harshly.
Sandra Fluke, a law student whom congressional Republicans would not let testify at a hearing on contraceptives, said if Republicans win in the fall, women will wake up to "an America in which access to birth control is controlled by people who will never use it, in which politicians redefine rape."
Clinton's speech marked the seventh consecutive convention he has spoken to party delegates, and the latest twist in a relationship with Obama that has veered from frosty to friendly. The two men clashed in 2008, when Obama outran Hillary Rodham Clinton's wife for the Democratic presidential nomination.
Clinton, then a New York senator, now Obama's Secretary of State, was in East Timor as the party met half a world away. She made a cameo appearance on the huge screens inside the Time Warner Cable Arena, though, turning up in a video that celebrated the 12 Democratic women senators currently in office.
Republicans have suddenly discovered a lot to like about Clinton â€" a man they impeached in late 1998 when they ran the House and he sat in the Oval Office.
Ryan made no mention of those unpleasantries when he told a campaign audience in Iowa, "Under President Clinton we got welfare reform. President Obama is rolling back welfare reform.
"President Clinton worked with Republicans in Congress to have a budget agreement to cut spending. President Obama, a gusher of new spending."
Independent fact checkers have repeatedly debunked the claim about Obama's welfare proposals. Nor did the Wisconsin lawmaker mention that under a balanced budget compromise with Clinton to rein in federal spending, Republicans agreed to create a new benefit program that provides health care for lower-income children and others ineligible for Medicaid.
The changes in the platform came after the Republicans criticized an earlier decision to strip out a reference to God.
Romney said that "suggests a party that is increasingly out of touch with the mainstream of the American people. ... I think this party is veering further and further away into an extreme wing that Americans don't recognize."
Romney had declared in a summertime trip there that Jerusalem was the country's capital. U.S. policy for years has held that the city's status is a matter for negotiations between Palestinians and Israelis, and Democrats said at the time he was pandering to Jewish voters in the United States.
The switch puts the platform in line with what advisers say is the president's personal view, if not the policy of his administration. "Jerusalem is and will remain the capital of Israel," it says. "The parties have agreed that Jerusalem is a matter for final status negotiations. It should remain an undivided city accessible to people of all faiths."
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