Waldman locates them:
Ryan has already demonstrated that when questioned about the fundamental dishonesty at the heart of Romney's tax plan—the contention that they can lower rates for everyone and pay for the whole thing by closing as-yet-unspecified loopholes for the wealthy—he flounders. And it's hard to blame him, because as William Gale of the Brookings Institution noted, it's tantamount to claiming Romney could drive from Boston to Los Angeles in 15 hours without breaking the speed limit, and there's just no convincing way to explain it. Add in Romney's false declaration in the first debate that his health care plan covers people with pre-existing conditions (it doesn't) and Ryan's own hard-right positions on topics like abortion and Medicare, and the congressman could spend much of the debate defending things that are hard to defend.
Tomasky gives Biden some free advice:
[Biden] needs to show that Ryan is a liar without calling him a liar. When Ryan said the other day that Democrats' new strategy was to call him and Romney liars, that was obvious pre-inoculation, so that if Biden utters the word, Ryan and the right can say Aha!, see, we told you, that's how desperate they are, etc.
The simple thing here is just not to use the word. Congressman, the facts suggest otherwise. Congressman, several studies all say. Congressman, I'm sorry, but that isn't the reality for most Americans. And so forth.
(Image from the Mansplaining Ryan tumblr)