Barack Obama will leave the White House and appear solo at a campaign event for Hillary Clinton in Philadelphia on Tuesday. His efforts to help revive a struggling Clinton come after many Democratic supporters say that the race has become uncomfortably close.

Clinton left a 9/11 ceremony in New York on Sunday and became unconscious while being forced into a private van. Her campaign said she was "overheated," but later revealed that she had been diagnosed Friday with pneumonia.

"I think the president's belief that she'd be an excellent president of the United States is something that you've heard him say many times. And I can tell you there's nothing that happened yesterday that has changed that assessment at all," Josh Earnest, Obama's spokesman said.

When asked about Clinton's use of the word 'deplorables' to describe Donald Trump supporters, Earnest said that there is a "disturbing tendency on the part of Republicans in Washington, D.C., to try to appeal to extremists for political support."