the advance or fail to advance the thesis that Mitt is just too defective to be president.
Don't explain, attack. But "you're a liar" is not a powerful attack in today's world.
Being a liar is such a minor charge these days that Romney is willing to trade off being an obvious liar for having the word "welfare" spoken more often.
I wrote something the other day about why the big lie works, and spent a lot of time thinking about how the big lie can be countered.
The big lie puts the opponent in a perpetually defensive posture on issue after issue. I think the key is to create a framework wherein the race is about who is a liar. Not who lost WWI for Germany, or who cut what out of medicare... who is too morally defective to hold the office.
It is hard to battle issues with a big liar so you must battle the man, and in particular his character.
Everyone already knows Obama can be president because he is. The burden of fitness is on Romney.
But to elevate Mitt's habitual lying to a decisive issue requires raising the stakes on what it means to be an habitual liar... that it is disqualifying. That is a strong statement, outside the usual, "He's a fine man who happens to have some bad ideas."
There is a little risk in putting it on the table because it would give the vapors to the centrist media clucks. But once it is on the table it cannot be reduced to "both sides do it."
Or rather, if it is reduced to that we win.
Romney cannot afford to argue that Obama lies as much as he does. First, he'd lose the argument. Second, even if he battled Obama to a draw on who's a big liar he cannot afford the election to be a referendum on Mitt because he is not a likable man.