Johnson faced no serious challenge for the nomination though Segregationist Alabama Governor George Wallace had surprising support.
Coinciding with a violent summer in the South, a big push to register black citizens to vote was undertaken as part of a movement known as Freedom Summer.
In Mississippi, black voters formed the Mississippi Freedom Democratic Party and sought to be seated as the delegates from Mississippi as the traditional party excluded black voters. Their effort received televised attention and could have embarrassed Johnson. Their struggle received some TV coverage but was preempted by a speech from the White House.https://www.youtube.com/watch?v=_TchoKJrvFQ
In the end, the Mississippi delegation walked out after the party refused the MFDP request but decreed that no future delegation would be admitted if it excluded black voters.