Hillary Clinton and Donald Trump return to campaigning after a July Fourth break. Both presidential candidates are visiting the battleground state of North Carolina, and for the first time in this race, Clinton will have President Obama by her side.

He will bring his former secretary of state to Charlotte on Air Force One, as her campaign seeks a lift from Mr. Obama with voters about four months to the general election. Clinton and Mr. Obama last traveled aboard Air Force One together on a 2012 trip to Burma, reports CBS News correspondent Chip Reid.

Her Republican opponent, Trump, is not happy about that.

Trump aired his grievances about the flight over Twitter Monday and asked, "Who pays?"

Why is President Obama allowed to use Air Force One on the campaign trail with Crooked Hillary? She is flying with him tomorrow. Who pays? — Donald J. Trump (@realDonaldTrump) July 4, 2016



In 2014, the Air Force, responding to a FOIA request, said the cost to taxpayers to operate Air Force One is $206,337 an hour.

In order to comply with federal election law, the Clinton campaign, according to the New York Times, will share the cost of the trip with the White House.

Clinton won't be traveling back to Washington with Mr. Obama after this afternoon's rally. She'll be campaigning in Atlantic City, New Jersey, on Wednesday.

Clinton is slightly more popular than her opponent, with 42 percent of those polled calling Trump "highly unfavorable," according to Gallup. The latest presidential poll from USA Today shows Clinton leading Trump by five points. That same poll found Trump trailing by double digits just two months ago.

Clinton's campaign could be bolstered by Mr. Obama's 51 percent approval rating.

"She was an outstanding secretary of state. She is my friend. I think she would be an excellent president," Mr. Obama said of Clinton at a 2015 news conference in Panama.

When Clinton lands in Charlotte Tuesday afternoon, she'll return to a state Mr. Obama won in 2008 but narrowly lost in his re-election effort. The joint appearance is Mr. Obama's pitch to all Democrats to rally around their candidate.

From Charlotte, Mr. Obama will praise Clinton's performance and is likely to unload on Trump, shutting down recent attacks from the presumptive nominee that claim the president is unable to fight terror effectively.

Back in May, Mr. Obama took aim from Japan.

"A lot of the proposals that he's made display either ignorance of world affairs or a cavalier attitude," the president said at the time.

On Friday Clinton will campaign with Vice President Joe Biden in the city where he was born -- Scranton, Pennsylvania.