It means "lacking in frankness, candor, or sincerity; falsely or hypocritically ingenuous; insincere" and is a great word to apply to many political statements. For example, Mitt Romney is railing against John McCain because McCain did not support the Bush tax cuts and did not vote to abolish the so called Death Tax.
I don't know about most middle income families, but the Bush Tax cut actually increased my income tax. I'm willing to bet that was the case for many. Oh, sure, some people got a tax reduction, but is wasn't people earning under $50,000 as nearly as I can calculate.
And the Death Tax? Just what percentage of people in the US have estates large enough to ever incur inheritance tax? 1%? 5%? The Death Tax is another case of a bill being sold to the public through disingenuous promotion. If I were Mitt Romney, I might be concerned about it. Me, I am more concerned with the mounting cost of fuel for my car and the rising cost of just about everything because of the cost of fuel.
So in this instance, I would say we should be giving kudos to John McCain, not holding him up for ridicule.