Obama "knows better than anyone there's more hard work to do" to fix the sputtering economy, said San Antonio Mayor Julian Castro, the convention keynote speaker, sharing the prime-time spotlight with first lady Michelle Obama.
After the deep recession, Castro said in excerpts released in advance of his speech, the nation is making progress "despite incredible odds and united Republican opposition."
He declared that 4.5 million jobs have been created since the president took office though that number refers only to private sector employment gains over the past 29 months and leaves out state and local government jobs that continue to disappear each month.
Obama was back home in the White House after a campaign appearance in Virginia earlier in the day. He said he'd be watching on television when his wife spoke.
There was no end to the appeals for donations to his re-election campaign, falling further behind Romney in cash on hand with each passing month. "If you think Barack's the right man for the job, please show your support with a donation of $5 or more today," the first lady emailed supporters a little more than 90 minutes before her scheduled speech.
Polls made the race for the White House a tight one, almost certain to be decided in a string of eight or 10 battleground states where neither the president nor Romney holds a clear advantage. And during the day there was ample evidence of an underperforming economy, from a report that said manufacturing activity declined for a third straight month to the Treasury's announcement that the government's debt exceeded $16 trillion at the close of the business day.
Castro, the first Hispanic chosen to deliver a keynote address, was unsparing in criticizing Romney, suggesting the former Massachusetts governor might not even be the driving force on the Republican ticket this fall.
"First they called it 'trickle down, the supply side," he said of the economic proposals backed by Republicans. "Now it's Romney/Ryan. Or is it Ryan/Romney?"
"Either way, their theory has been tested. It failed. ...Mitt Romney just doesn't get it," Castro said. Romney's running mate is Wisconsin Rep. Paul Ryan.
The divide over taxes goes to the core of the campaign.
Romney and the Republicans favor extension of all of the existing Bush-era tax cuts due to expire on Dec. 31, and also want to cut tax rates 20 percent across the board.
Obama, too, wants to keep the existing tax cuts in place except for people with earnings of $250,000 a year or more.
Delegates in the convention hall cheered whenever Obama's image showed on the huge screen behind the speaker's podium, and roared when the late Sen. Edward M. Kennedy was shown mocking Romney in their 1994 Senate race.
"On the issue of choice, I am pro-choice, my opponent is multiple choice," the late senator said as cheers grew louder.
Romney supported abortion rights while serving as governor; he opposes them now.
Democrats unspooled insult after insult as they took their turn the week after the Republicans had their convention in Tampa, Fla.
Illinois Gov. Pat Quinn said that Republicans had omitted mention of Romney's term as Massachusetts governor at their gathering.
"We already knew this extremely conservative man takes some pretty liberal deductions. Evidently that includes writing off all four years he served as governor," Quinn declared.
Said Senate Majority Leader Harry Reid of Nevada, speaking of Romney: "Never in modern American history has a presidential candidate tried so hard to hide himself from the people he hopes to serve."
"When you look at the one tax return he has released, it's obvious why there's been only one. We learned that he pays a lower tax rate than middle-class families. We learned he chose Swiss bank accounts and Cayman Island tax shelters over American institutions."
Obama, by contrast, was lauded for helping win approval of health care legislation and for supporting abortion rights and gay marriage.
"He said he'd take out bin Laden, and with our great SEAL team, he did," added Tim Kaine, former national party chairman and Virginia governor, now running for the Senate.
In his campaign trip to Virginia earlier in the day, Obama told an audience at Norfolk State University that the economy will get worse if Romney wins the White House this fall and that Election Day apathy was his enemy and theirs.
Republicans are "counting on you, maybe not to vote for Romney, but they're counting on you to feel discouraged," he said. "And they figure if you don't vote, then big oil will write our energy future, and insurance companies will write our health care plans, and politicians will dictate what a woman can or can't do when it comes to her own health."
On the final stop of a pre-convention campaign circuit of several battleground states, the president also dropped off a case of White House-brewed beer at a local fire station.
A few hours later and hundreds of miles distant, Rep. Debbie Wasserman Schultz of Florida, the Democratic party chairwoman, opened the three-day convention to the cheers of delegates.
The Time Warner Cable Arena's conversion to the Democrats' made-for-television convention hall was complete. The lectern rested on a blue-carpeted stage, inside a circle of white stars suggestive of the presidential seal.
The Republican challenger was in Vermont as the Democratic convention began, preparing for three fall debates with Obama almost certain to be critical to the outcome of the election.
To laughter from his Virginia audience, Obama explained why he was ceding the opening-night spotlight to his wife.
"A political convention is "just like a relay, and you start off with the fastest person," he said.
"So I'm going to be at home and I'm going to be watching it with our girls. And I'm going to try not to let them see their daddy cry, because when Michelle starts talking I start getting all misty."
There was no shortage of political calculation behind the program of the convention's first night or for any other. Polls show the first lady is more popular than her husband.
Democratic delegates bestow their nomination on Obama and Vice President Joe Biden on Wednesday night, the same night that former President Bill Clinton delivers a prime-time speech aimed at voters disappointed with the results of the past four years yet undecided how to cast their ballots.
White men favor Romney over Obama in public and private polls, but a Gallup survey taken in July showed that 12 years after leaving office, Clinton was viewed favorably by 63 percent of the same group and unfavorably by only 32 percent.
Obama's acceptance speech caps the convention on Thursday night at the 74,000-seat Bank of America football stadium. Aides kept a wary eye on the weather in a city that has been hit in recent days with strong afternoon rains.
Republicans did their best to rain on Obama's convention, whatever the weather.
Vice presidential candidate Paul Ryan spoke in Westlake, Ohio, standing behind a lectern bearing a sign that read "Are you better off?"
Republicans released a web video that interspersed images of Obama and the economy's weak performance with slightly out-of-focus video clips of former President Jimmy Carter discussing the nation's economic woes when sat in the Oval Office more than 30 years ago.
Officials said Republicans were stockpiling cash for the fall campaign. Romney raised more than $100 million for the third month in a row in August, officials said.
(Copyright 2012 by The Associated Press. All Rights Reserved.)