Staraight Talk, Straight Action

McCain was still married and living with his wife in 1979 while, according to The New York Times' Nicholas Kristof, "aggressively courting a 25-year-old woman who was as beautiful as she was rich." McCain divorced his wife, who had raised their three children while he was imprisoned in Vietnam, then launched his political career with his new wife's family money.

Link.

Glen Greenwald gives the religious context:

How can John McCain claim to believe that the law should recognize only "traditional marriages" while simultaneously demanding that the law recognize his own so-called "second marriage" -- also known as "an adulterous relationship" under the precepts of "traditional marriage" (Mark 10:11 -- "And he said to them, "Whoever divorces his wife and marries another, commits adultery against her").

As I noted in a recent comment, while dishonesty and a detachment from truth is a common trait of just about all politicians, the radical rightist America-haters of the GOP have taken that to a historical extreme. This just goes to show that these guys can't even be straight about, well, straight marriages. (See the first link for more about that.)