克林顿突发肺炎后准备重返总统竞选活动

Hillary Clinton plans to return to the campaign trail Thursday after abruptly leaving a 9/11 memorial event in New York City Sunday, which her campaign at first said was due to overheating but later attributed to a pneumonia diagnosis she received Friday.

A video of the incident posted online shows Clinton propping herself up on a street bollard before stumbling into a waiting van with the help of Secret Service agents and her aides.

In a statement, her campaign said Clinton will be in Greensboro, North Carolina, Thursday to "discuss her vision for an America that is stronger together."

While Clinton continued to recuperate, she got a rousing endorsement from the country's number one Democrat and her former boss -- President Barack Obama.

"I am really into electing Hillary Clinton," Obama told cheering supporters in Philadelphia Tuesday. "I have seen how smart and savvy and tough she is. I had a front row seat for four years," Obama said of his former secretary of state.

Obama mocked Republican candidate Donald Trump, saying he "is not in any way, shape or form fit to represent this county abroad and be our commander-in-chief."

He belittled Trump's praise for Russian President Vladimir Putin as "a strong leader, because he invades smaller countries, jails his opponents, controls the press and drives his economy into a long recession."

Trump fired back at Obama on Twitter, accusing the president of allowing Russia to invade Crimea. "Russia took Crimea during the so-called Obama years," Trump said. "Who wouldn't know this and why does Obama get a free pass?"

The latest polls show the race between Clinton and Trump tightening, with Clinton holding a 3- to 4-point lead.