President Obama joins Clinton to campaign in North Carolina

In her June 2008 concession speech for the Democratic U.S. presidential nomination, Hillary Clinton pledged to do all she could to propel Barack Obama to the White House. On Tuesday, he returns the favor.

After months of waiting on the sidelines while his former secretary of state battled Senator Bernie Sanders to be this year's Democratic nominee, the president and Clinton arrived in Charlotte, North Carolina, in what is likely to be the first of many trips to urge voters to pick his onetime rival as his successor.

Obama endorsed Clinton last month with a forceful video in which he stated that no one had been so qualified for the job. But a joint appearance planned for soon after that was postponed after the mass shooting on June 12 at a gay nightclub in Orlando, Florida.

"You will hear from him at length today about why he is so enthusiastic about her candidacy and why he thinks she would be an excellent 45th president of the United States," White House spokesman Josh Earnest told reporters before the event on Tuesday.

Clinton hopes to reclaim North Carolina for Democrats in the Nov. 8 election. Obama won the state in the 2008 general election but lost it narrowly in 2012.

However, Clinton's trip with Obama could be overshadowed by FBI Director James Comey's announcement on Tuesday that the agency will not recommend she face charges over her use of a personal email server while she was secretary of state.

Clinton's campaign welcomed the end of a probe that has cast a cloud over her campaign, but Republicans seized on Comey's criticism of what he termed Clinton's "extremely careless" handling of emails. Presumptive Republican nominee Donald Trump, who was also due to campaign in North Carolina on Tuesday, said of the FBI recommendation, "As usual, bad judgment."

Earnest said on Tuesday that Obama did not get advance notice of Comey's announcement and that he would not discuss the FBI investigation with Clinton.

Obama's first campaign appearance with the former first lady will close a circle on a relationship that started cordially when the two were colleagues in the U.S. Senate, grew tense when they were rivals in the 2008 race, and became close when Clinton was secretary of state during Obama's first term.

Clinton and her family have played a role in Obama's elections. Clinton and Obama appeared together in Unity, New Hampshire, following their divisive primary fight in 2008, and Clinton's husband, former President Bill Clinton, gave a well-received speech at the 2012 Democratic convention.

Obama has focused on what he touts as Clinton's strength of character, in hopes of shoring up support among voters who find her untrustworthy, a weakness Trump has sought to exploit.

Clinton needs Obama to woo young and left-leaning voters who backed Sanders and who made up part of the president's voting coalition in 2008 and 2012. Clinton has also campaigned with high-profile liberal U.S. Senator Elizabeth Warren, and she will appear later this week with Vice President Joe Biden.

She and Obama traveled to North Carolina on the presidential plane Air Force One, a move Trump said was a burden on taxpayers. A Clinton spokesman said the campaign would cover its portion of the travel costs.

(Reporting by Jeff Mason, additional reporting by Emily Stephenson and Ayesha Rascoe; Editing by Frances Kerry and Jonathan Oatis)