The contents of Romney's tax returns: What would be able to brush off?

[Absentee Voting Ghost of Ruin]

Here are my thoughts:

Easy to brush off:
-In substantial debt
-Failure to donate the expected tithe to his church
-Did business with Iranian government

Likely to make a dent in Rom's election performance:
-that he's wealthier then he claims to be
-proof that he was working for Bain for longer then he claimed
-direct ties to extremely impolitic companies

Almost certainly fatal to Rom's election chances:
-Evidence of offshoring and other tax evasion
-having(legally) paid relatively little in taxes thanks to loopholes

Personally, I suspect it's some combination of the last two. IMO, having the next three months full of commercials that say, "Mitt Romney is worth a quarter of a billion dollars and he paid less taxes than the average McDonald's employee," would be completely and utterly devastating.