Donald Trump knows he can’t handle a debate against Joe Biden, and he thinks he’s found his way out, according to a formerly conservative columnist. Columnist Jennifer Rubin — a conservative until Donald Trump came along — appeared on MSNBC on Sunday, where she was asked about Fox News’ recent attack against Biden. Specifically, Fox hosts have been claiming that Biden is “jacked up” and needs to be drug tested before any debate with Trump. “Come on,” the host said to Rubin after playing a clip from the conservative network. Want more breaking political news? Click for the latest headlines at R…