Electoral overnegation
This post from Amy Hamblin's Community Blog was on the front page of the Obama-Biden web site for a while last night:
We're still awaiting the final results tonight, but one thing is clear — this grassroots movement can never be underestimated. Thank you to everyone who helped us make an astounding 1,053,791 calls today! I know it wasn't easy and many of you kept calling long after you were tired and your voice had grown hoarse, but your calls to get our supporters out the polls helped tip the scales in key battleground states like Pennsylvania and Ohio. [emphasis added]
We've discussed the general phenomenon of overnegation — semantic problems typically arising from the combination of modals, negatives, and scalar predicates — many times in the past. The particular case of cannot/must not underestimate/overestimate is discussed here, here, and here.