Sarah Palin's speech tonight exists within a weird middle ground between fairly low expectations and a fairly high degree of difficulty.
Voters have questions about Palin's background, her governing philosophy, her readiness to lead, and her position on a variety of specific issues. It will be impossible to address all of these within the context of a single speech -- particularly for someone who had never spoken to a national audience before last Friday. On the other hand, the pundits, recognizing the rough couple of days that she's had in the press, will most likely be inclined to react sympathetically toward her. So may voters at home, buoyed by what will inevitably be an enthusiastic response in the Xcel Center.
Under these circumstances, it will be imperative for Palin not to overreach. I would avoid any specific claims -- like her arguably false claim in Dayton on Friday that she opposed the Bridge to Nowhere -- that won't hold up to a FactCheck.org vetting. And I wouldn't make any assertion to expertise in foreign policy. A claim, for instance, along the lines of what Cindy McCain said the other day -- that Palin is a foreign policy expert because Alaska is close to Siberia -- will ring hollow even if articulated well, and if articulated poorly, could easily become her Potato-e moment. The debate against Joe Biden, which Palin will have much more time to prepare for, is a better forum than that, an opportunity to demonstrate rather than assert her working knowledge of foreign policy.
I do think she has to convey a certain seriousness of purpose -- one overly cute reference to mooseburgers is probably one too many -- but there are ways to do that without invoking foreign policy, such as talking about "small town values". A throwaway applause line or two critiquing the media is probably worthwhile, so long as it seems good-natured rather than defensive.
But basically, she shouldn't try and do too much. If she pours the media half a glass, they'll most likely be inclined to call it full.