St. Louis police said the 55-year-old attorney was assaulted at about 8:30 a.m. during a verbal altercation in the 1200 block of Market Street near City Hall.
"The likelihood that Yellow will survive is increasingly bleak," an International Brotherhood of Teamsters letter sent Friday to the union's members said.
Former Democratic Gov. Jay Nixon of Missouri is joining No Labels’ effort to lay the groundwork for a centrist third-party presidential ticket in 2024.
An excessive heat warning is in effect through Saturday for the St. Louis area. Afternoon temperatures may feel as high as 110 degrees, especially in the city.