The percentage of Democrats who say they would vote for former Vice President Joe Biden if the presidential race were held tomorrow slipped by 10 points after the first primary debate. According to a Morning Consult/FiveThirtyEight poll of likely Democratic voters released on Friday, 41.5 percent said before the debates they would vote for Biden tomorrow, but 31.5 percent said the same thing after Thursday night's debate. The apparent decline in support comes after Biden was widely seen as having faltered, including engaging in a stark exchange with Sen. Kamala Harris (D-Calif.) over school busing. Harris herself got a nearly...