Not to condone his behavior but it isn't out of the ordinary for politicians.
I don't know if there is some legal obstacle that is delaying his getting married again--or if the claim that they are "engaged" is just a sham and he feels that the public doesn't (by and large) hold cohabitation without marriage against politicians nowadays.
And we let it get to the point where it doesn't matter anymore....we just keep dropping our standards more and more, it's no wonder we find ourselves where we are now.