Heidi M Przybyla

USA TODAY

President Obama was let loose on the 2016 campaign trail for the first time Tuesday, giving Hillary Clinton the detailed and enthusiastic character testimonial her campaign hopes will unite the Democratic Party before its convention in Philadelphia later this month.

At a Charlotte rally, Obama spent a significant amount of time in his first joint campaign appearance this year with Clinton vouching for her personal attributes, citing her work on child health and poverty issues as a young lawyer and her work on his behalf after losing a protracted 2008 primary. He also noted her popularity among Democrats and Republicans when she served in the U.S. Senate and as secretary of State.

“I saw how she treated everybody with respect, even the folks where weren’t, quote unquote, important,” he told supporters. “That’s how you judge someone is, how do they treat somebody when the cameras are off, and they can’t do anything for you,” said Obama, before outlining the stakes in the 2016 election while stressing Clinton’s economic plan.

The joint campaign appearance of the two former rivals came not long after the FBI announced a decision on an issue that has been a cloud over her campaign for more than a year: her use of a private email server while serving as Obama's secretary of State. FBI Director James Comey announced Tuesday morning that, while Clinton and her staff had been "extremely careless" in their handling of classified information, his recommendation was that Clinton should not face criminal charges.

Neither Obama nor Clinton, who spoke before the president, mentioned the announcement by the FBI. However, the Clinton campaign issued a statement earlier in the day: “We are pleased that the career officials handling this case have determined that no further action by the Department is appropriate,” said spokesman Brian Fallon.

Clinton is hoping the president will energize critical Democratic Party demographic groups she’s struggled to win over, namely young voters who powered his wins in 2008 and 2012. In this year's Democratic contest, young voters were overwhelmingly behind Vermont Sen. Bernie Sanders, who has yet to officially endorse Clinton and remains critical of her on some issues, such as Wall Street regulation.

The Clinton campaign chose North Carolina — one of the few battleground states where presumptive Republican nominee Donald Trump has a tiny polling advantage over Clinton — for Tuesday's rally in an attempt to show she’s on the offense early in the general election. In 2008, Obama was the first Democrat to win the state since 1976, though he lost to Republican Mitt Romney in 2012. The state is considered a must-win for any Republican candidate.

Clinton’s core challenge in the general election against Trump is voter perceptions of her trustworthiness, according to polls, a problem that’s been amplified by the FBI’s investigation and one on which Trump is capitalizing by calling her “crooked.”

The announcement by the FBI earlier Tuesday may have fed the crowd's enthusiasm. News broke about the time 83-year-old Manache Ragsdale of Charlotte started her two-hour wait in line to get into the hall on a day when temperatures topped 90 degrees before lunch. “I was elated, very happy and relieved,” Ragsdale said.

Clinton herself has acknowledged she has work to do on the trust issue. “Can I be blunt?” said Obama near the end of his speech. “The fact is, Hillary is steady and she is true,” he said. “We don’t care about the slings and arrows that are thrown at us because we know that’s how real change and real progress happens,” he said. He added: “We weren’t born with a silver spoon,” one of many veiled digs at Trump.

Seemingly relishing his first appearance on the 2016 campaign trail, Obama contrasted Clinton’s experience as a senator and on foreign policy with Trump throughout the speech, at one point even comparing Trump’s Twitter habits to that of his 15-year-old daughter. “Sasha tweets but she doesn’t think that she thereby should be sitting down at the desk,” he said, referring to the Oval Office. “Hillary Clinton has been tested, she has seen up close what’s involved in making those decisions.”

The president was particularly focused on Clinton’s economic message. “If your concern is who’s going to look out for working families, if you’re voting your pocket book, if you’re asking who’s actually going to stand up for the guy on the construction site,” said Obama, “If that’s your concern, this isn’t even a choice because the other side has nothing to offer you.”

'Extremely careless,' but FBI advises no charges for Clinton's emails

Obama released a video as the two jetted south on Air Force One for the event that focused on Clinton's character. “Not only did she impress me during the campaign, but she frankly really impressed me in terms of how she handled the loss of that primary. She was a trooper,” he said of their 2008 Democratic presidential race, which Obama won narrowly.

Obama endorsed Clinton on June 9, days after she locked up the delegates needed to secure the Democratic presidential nomination.

Clinton campaign 'pleased' with FBI decision on emails

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Clinton and Obama have been trying to campaign together since an initial joint appearance in Wisconsin was cancelled after the Orlando shootings. Obama's approval rating has inched to 50% or above in recent polls, something Democrats hope will help Clinton and other party officials running down the ballot.

Clinton's favorable rating was 42% in a recent USA TODAY/Suffolk University poll, while Trump was at 31%. Clinton gave a detailed defense of Obama's record in her remarks, saying he saved the nation from a second Great Depression.

Some people in the crowd who had voted for Obama in the 2008 primary said afterward the president’s speech made it that much easier to back Clinton in 2016.

“It answered a lot of questions about Hillary,” said Linda Edwards, a 67-year-old retiree from Charlotte. “The strongest endorsement you can possibly get is from the president. … He won me over.”

“It just strengthened my resolve that she is the person we need in the future,” said Jason Harwood, an elementary music school teacher from the small central North Carolina town of Rockwell who also backed Obama eight years ago.

During her remarks, Clinton took several swipes at Trump, who was a leading advocate of conspiracy theories that Obama is not an American-born citizen.

USA TODAY/Suffolk Poll: Clinton's lead over Trump narrows to 5 points

Obama is "someone who has never forgotten where he came from and Donald, if you are out there tweeting, it’s Hawaii," she said.

Contributing: Mark Barrett, The (Asheville, N.C.) Citizen-Times, reporting from Charlotte