Brian Steinberg Senior TV EditorAndrea Mitchell almost drowned in balloons when she covered the 2008 Republican National Convention, and was forced to swat them away as she tried to tell MSNBC viewers what was taking place on the ground.In 2020, the longtime NBC News and MSNBC correspondent will have plenty of air.Fewer TV journalists will be on the ground at either the Milwaukee site previously selected for the Democratic National Convention or the Jacksonville or Charlotte venues Republicans