'Hopeful' Obama asks for four more years CHARLOTTE, N.C. -- After nearly four years in office, President Barack Obama asked America on Thursday night to give him a second term, in a speech reaching back to the touchstone of "hope and change" that propelled him to the White House in 2008, while also acknowledging the unfinished work in achieving that promise. President Barack Obama accepts the Democratic presidential nomination and addresses the DNC, Thursday, in Charlotte, N.C. In his formal acceptance speech, the president embraced the contrast that his party had tried to draw between himself and Republican presidential candidate Mitt Romney throughout this week's Democratic National Convention. Obama said the GOP only offered voters the "same prescription they've had for the last thirty years," and laid out policies that he said would move America in the direction of Obama's campaign theme: "Forward." I recognize that times have changed since I first spoke to this convention. The times have changed ... I'm no longer just a candidate. I'm the president," Obama told the crowd at Charlotte's Time Warner Cable Arena, where his speech was moved after weather concerns disrupted plans for an outdoor event. Slideshow: Democratic National Convention "But as I stand here tonight, I have never been more hopeful about America," the president added, in a line emblematic of his efforts to once again stir enthusiasm in his candidacy. The speech capped a convention designed to reignite enthusiasm with Obama's winning voting coalition from 2008, including dozens of speeches paying testament to the president's character and condemning Romney in the same breath. Chris Keane / Reuters President Barack Obama addresses the final session of the Democratic National Convention in Charlotte, North Carolina September 6, 2012. On foreign policy, for instance, Obama ridiculed Romney as inexperienced and naïve. "After all, you don't call Russia our number one enemy - and not al Qaida - unless you're still stuck in a Cold War time warp," he said. You might not be ready for diplomacy with Beijing if you can't visit the Olympics without insulting our closest ally. Related: Four challenges for Obama The Democratic convention this week was constructed in part to rebut last week's Republican National Convention in Tampa, Fla., during which Romney seized on disappointment in Obama after four years, and argued "the time has come to turn the page." Convention speeches have served as major milestones for Obama in his path to the White House. His 2004 keynote speech as a Senate candidate rocketed him to national stardom, and Obama's 2008 speech as the Democratic presidential nominee helped propel him to victory. On Thursday evening, Obama nodded toward the disillusionment of the high-soaring rhetoric of his last campaign, but said that he was still moved by the "hope" that animated his 2008 bid, and asked for more time to achieve his goals. You didn't elect me to tell you what you wanted to hear. You elected me to tell you the truth," he said. And the truth is, it will take more than a few years for us to solve challenges that have built up over decades. Republicans, including Romney, have made issue of that tarnished sense of hope. The GOP nominee, who said he didn't plan to watch Obama's speech, nonetheless expected it to dwell on "forgotten promises." Romney's campaign manager said Obama's speech had only made "the case for more of the same policies that haven't worked for the past four years." Republican-leaning super PACs and the state of the economy are two issues causing concern for President Obama's re-election campaign as the Democratic National Convention wraps up in Charlotte, North Carolina. NBC's Kristen Welker, Chuck Todd, and Tom Brokaw report. But tonight's acceptance speech was characteristic of a convention that devoted much of its energy to building up Obama and knocking down Romney. Vice President Joe Biden's speech earlier in the evening was, in many ways, a warm-up act for the president, with Biden serving as the "character witness" for Obama. The vice president hailed Obama's "gutsy" decisions, from rescuing the auto industry to ordering the mission to kill Osama bin Laden. And he made the case that the both of them had more work to do in a second term. We know we have more work to do. We know we're not there yet. But not a day has gone by in the last four years when I haven't been grateful that Barack Obama is our president," said Biden, "because he always has the courage to make the tough decisions." Biden also assumed the more traditional role for a vice president by going aggressively after Romney and his ticket-mate Paul Ryan -- keeping with the constant stream of scrutiny leveled toward the Republican duo at this week's convention. "Folks, the 'Bain Way' may bring your firm the highest profits," said Biden, referring to the private equity firm Romney had co-founded, experience from which the GOP nominee cites as a chief credential. But it's not the way to lead our country from the highest office. The notion of conviction was also a theme in Sen. John Kerry's foreign policy-oriented speech earlier in the evening. The 2004 Democratic presidential nominee said Romney "hasn't learned the lessons of the past decade," referring to the wars in Iraq and Afghanistan initiated by President George W. Bush. Kerry also accused Romney of reversing himself and being inconsistent in criticizing Obama's handling of Afghanistan and Libya. "Talk about being for it before you were against it," exclaimed Kerry, riffing on the infamous line from his 2004 campaign that fueled charges that Kerry - like Romney now - was a "flip-flopper." Obama's speech - along with Romney's last week - marked a turning point in the 2012 campaign, which now heads into its most intense leg leading up through Election Day. Convention speeches are regarded as some of the few opportunities for candidates to affect the trajectory of the race, though it will take days, if not more, to know whether the dueling powwows in Tampa and Charlotte will have moved the needle at all. Both campaigns will hit the road on Friday to begin making their cases until a series of debates in October - the next major turning point in the campaign - one that could help determine the outcome of the election. On Friday, Obama and Biden will campaign together in both Iowa and New Hampshire, two key swing states that their ticket won in 2008. Romney, meanwhile, will campaign in New Hampshire while vice presidential nominee Paul Ryan campaigns in Nevada. Win Mcnamee / Getty Images Democrats gather in Charlotte, N.C., to officially nominate President Barack Obama and Vice President Joe Biden as the party's candidates for the 2012 presidential election.