It turned out to be no whitewash, despite the fact that there was a softening approach to Teddy. The most important thing the film did was show that Mary Jo suffocated, not drowned, and that made his inaction inexcusable. And Joe Gargan's reproach to Teddy before his speech also was where the film by default came down.
Basically the film depicted Teddy as taking the dishonorable way out so he could finally have his father's approval as someone "great". While the film took dramatic license in showing Joe Kennedy still active enough mentally to exercise that control, the underlying subtext I think was brilliant. Yes, Teddy came off with some not completely unsympathetic nuance, but it didn't overshadow the film's ultimate by default negative spin.

A reading of some things the producer says leads to me to believe that. He claims it's about "what he had to go through." It seems like its mostly going to be about how it negatively affected his career . . .
http://freebeacon.com/politics/chappaquiddick-producer-viewers-will-see-what-ted-kennedy-had-to-go-through/

Perfect time to whitewash his crime. So many younger people are ignorant of the facts. We'll see.

Wouldn't surprise me to see them somehow try to absolve Kennedy of all wrongdoings. I'll wait to see though.

Well let's wait to see how it is portrayed. It could be made to make Ted Kennedy look sympathetic in that her death was a complete accident and that he spent hours trying to save her. It could be used to try and rehabilitate Kennedy's image instead of tear it down. We will see how they showcase the event and Kennedy's action in it.