Can any Republican truly challenge Trump?

First: Republican candidates got busy bruising each other last night in a chaotic debate marked by insults, prepared one-liners and plenty of pettiness. But it offered little clarity about who, if anyone, can beat Donald Trump?  Plus: Today is day one of the impeachment inquiry into Joe Biden. Republicans promise a show and tell. Democrats ask, where's the evidence?  And: President Biden is in Arizona to revive a 2020 and 2022 campaign theme that Democrats believe worked: MAGA extremists are a singular threat to American democracy.  To learn more about how CNN protects listener privacy, visit cnn.com/privacy Learn more about your ad choices. Visit podcastchoices.com/adchoices