I keep reading this as some kind of a bizarre excuse for Newt's behavior.
My marriage vows included an oath to forsake all others.
Newt is guilty of lying under oath as well.
I disagree with your assessment. He violated his oath, he didn't lie. I say that because I believe at the time he took his oath, he meant it. I can't prove that, obviously, but just because you don't keep a promise doesn't mean you lied about it, although we use that term a lot regarding promises.
If you think he never intended to keep his marriage vow, then I you could say he lied, which is why I simply say I disagree with your assessment.
But I'm not making excuses for him. Pointing out that a person didn't commit a crime doesn't excuse him for something else he DID do.
Lying under oath in a criminal or civil case is a crime. Maybe unfortunately, breaking your marriage vow is not considered a crime anymore.
BTW, this is one of my strong points for Mitt -- he hasn't, so far as anybody can see, broken his marriage vow, nor does he seem likely to.
I'm not saying other candidates can't say the same, but I know several who cannot.