There will always be instances where campaign personnel disagree with one another and fight amongst themselves. Simply replacing Lewandowski won’t do anything to help the Trump campaign stop the slide if Trump does not have some kind of epiphany and come to realize that he is the root of his problems.
I think it will take the likes of leaders such as former New York mayor Rudy Giuliani and New Jersey Gov. Chris Christie to help Trump develop a credible approach that he can carry through the general election. Unless Trump changes and begins to define a rational basis for his campaign, he will never have the legitimate appeal needed for a winning coalition.
So far, there is still no sign that Trump sees himself, what he thinks and how he expresses himself as the real problem.