Ed Harris looks nothing like John McCain

It was close enough. Think of all the placeholder JFKs and Elvises over the years. Not to mention that when actors look too much like the people they play the production is often criticized for just being a reenactment without any actual depth.

It's pretty common in biopics for actors to not to look that much like the people they are playing so I'd argue the voice is the much bigger issue. I get not wanting to do a straight impersonation but adopting some of the mannerisms, voice inflections & cadences couldn't hurt & Ed Harris didn't really do any of that. Their voices are about as different as you can get. Ed Harris' voice is deep & slightly gruff & while McCain had a distinct, nasally & higher pitched tone that was easily recognizable. There would be no way to tell who Ed Harris was playing without context.

The movie is about Sarah Palin, Not John McCaine. They wanted to get the Looks, Personality and Voice down perfect for Palin and they nailed it. Also Ed Haris was good enough and they got the look pretty similar. The voice sure that was mehhh, but everything else was fine.