Is John McCain legally married to Cindy McCain ?

In this video CNN found out that John McCain applied for a marriage license with Cindy before he was divorced from his first wife Carol McCain. They also found that he was having an affair with Cindy for 9 months while he was married and still living with his first wife Carol McCain. Does this make the marriage between John and Cindy McCain null and void ? If John was elected would Cindy be considered the First Mistress ? What does this say for marriage and for our potential first family ?