If we didn't know him better we'd think he was on amphetamines. As it is, I suspect we're seeing the effects of extreme tiredness and intense pressure on the Romney frontal cortex:
This reminds me of something that was once said of Romney's father George, a former governor of Michigan (the Romney family has deep ties to the state, hence Mitt's crazed riff): that watching him campaign was "like watching a duck make love to a football".
Michigan votes today. It's a huge moment for Romney, a must-win. The polls suggest it will be extremely close.