What's happening today on the campaign trailVice President Kamala Harris is brushing off former President Donald Trump's suggestion that they debate on Fox News on Sept. 4, saying that it's a "safe space" for him and that she intends to show up on Sept. 10. Trump said last week that he agreed to Fox News' formal invitation to host a debate and would no longer participate in a planned ABC debate arranged by the campaigns for Trump and President Joe Biden. He also lobbed criticism at ABC.Harris is reaching the homestretch in her search for a running mate, reportedly having held meetings with several top contenders in recent days. She is expected to rally alongside her vice presidential pick in Philadelphia tomorrow.