First Lady Michelle Obama fired the first shots at the Democratic convention with an impassioned speech backing her husband, President Barack Obama.
Her address on Tuesday came as Republicans sharpen their attacks on Obama after he gave himself an "incomplete" grade for his management of the economy in his final rally before accepting the Democratic Party nomination.
Michelle Obama spoke of the couple's shared background in struggling families.
She also noted the "extraordinary privilege" of serving as first lady.
She said that four years ago she "believed deeply" in her husband's "vision for this country" but worried about how a run for president would change their life and the life of their daughters.
"Barack and I were both raised by families who didn't have much in the way of money or material possessions but who had given us something far more valuable - their unconditional love, their unflinching sacrifice, and the chance to go places they had never imagined for themselves."
"As president, you can get all kinds of advice from all kinds of people," she said "But at the end of the day, when it comes time to make that decision, as president, all you have to guide you are your values and your vision and the life experiences that make you who you are."
She said Obama "just keeps getting up and moving forward… with patience and wisdom, and courage and grace."
Al Jazeera's Patty Culhane, reporting from the convention said Michelle Obama's speech had a simple message.
"Her message was obvious, her husband maybe the president of the USA, but he's a normal guy," said our reporter.
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Also on Tuesday San Antonio Mayor, Julian Castro delivered the keynote address.
Former White House Chief of Staff Rahm Emanuel said the next president would set the tone for the next 40 years.
"It will be the president's leadership that determines how we as a nation meet the challenges that face the middle class. It is the president's values that shape a future in which the middle class has hope," said Emanuel.
Michelle's speech came four years after she vowed - before a stadium full of delegates in Denver, Colorado - that Barack Obama, despite his "funny name", would make an "extraordinary president".
Today, with economic malaise casting serious doubt on that claim, Democrats face a glut of Republican charges that, though his election was historic and rightly celebrated, Obama's presidency has been a bust.
Obama was asked to grade his performance on the economy during an interview with a Colorado news programme broadcast on Monday and unwittingly provided an opening for his opponents.
"You know, I would say 'incomplete'," Obama said, before laying out steps he had taken to save the auto industry, make college more affordable and to invest in clean energy and research, which he said were important for the long term.
Paul Ryan, the Republican vice presidential nominee, exclaimed with incredulity on CBS News: "Four years into a presidency and it's incomplete?"
Obama's comments followed another stumble by his team at the weekend, when top officials laboured over the answer to a seemingly straightforward question: "Are Americans better off now than they were four years ago?"
But with the campaigns moving into the final stretch after this week's Democratic convention, it is the Republicans that appear to have ground to make up in the White House race.
National polls put the rivals neck-and-neck, but a closer inspection of swing states reveals that Romney has his work cut out, especially as the poll bounce Republicans were hoping for after their convention last week in Tampa, Florida, failed to materialise.
'Road to Charlotte'
Obama will use the convention to defend his quest for change, highlighting his historic health care reform and his orders to end the ban on gays serving openly in the military, to withdraw troops from Iraq, to decimate al-Qaeda and kill Osama bin Laden.
The 51-year-old graying president will seek to rekindle some 2008 magic on Thursday as he leaves the confines of a convention hall for a huge outdoor football stadium packed with 70,000 people.
Obama will call for higher taxes on the rich and for safeguarding health care for the elderly, hoping to come off as more sympathetic to the middle class than that of multi-millionaire Romney, the 65-year-old former Massachusetts governor.
On Wednesday Bill Clinton, a hugely popular former Democratic president remembered for steering a more prosperous age, will take the stage for a highly anticipated speech making the economic case for four more Obama years.