It had a fair amount if impact, particularly popular opinion which lead to the end if his political career.

Johnson was wildly ambitious, and a force of nature in the senate. He wanted to be president but when he realized that Kennedy would win the nomination he made a deal. Kennedy and Johnson didn't like each other, but Kennedy needed Johnson support and skills, and Johnson wanted to be set up to run for pres, what better place than vp.

I think we all know what happened. Johnson became president and fairly popular at the time. He set forth the war on poverty, continued the civil rights movement among other things. He also went into Vietnam which was a popular thing at first.

Problem is times were a changin. A new counter culture was rising and the media was changing too. Horror stories of Vietnam started coming back, young men that didn't want to fight and had different ideas than their fathers were being drafted and coming home hurt and angry. The tide was turning and Johnson was largely seen as the one to blame.

Probably the example that most displays this is a famous quote by Johnson himself.

Walter Cronkite was the face of American news in a way you can't imagine today. He was completely trusted and the guy that an entire nation looked to for current events.

Cronkite took a trip to Vietnam and reported on it. It was a damning negative piece that concluded with Cronkite calling the war un-winnable

Johnson saw this broadcast, after watching it he said that "if I lost Cronkite I lost middle America"

Johnson was right. Not long afterward Johnson announced that he wouldn't run for reelection.

This opened up the opportunity to an equally ambitious and presidential obsessed man to run and win the election, Richard Nixon.