No you're both wrong. We've never actually even hit 70% in the post-WWII period.
Bush jacked it up to post-war record levels of just under 68%. Here's a good graph of the debt that someone put together:
http://www.cedarcomm.com/~stevelm1/usdebt.htm
Figure 3 on there shows the spending/revenue relationship among the last 45 years of Presidents.
Finally, Figure 4 give us what we need. Now, granted GDP will fall by about 1.5% this year from $14.3T down to about $14.1T. And considering we were looking at a $500B deficit before the stimulus, after factoring in some early increased tax revenue generated by the stimulus, we can expect about a $1T deficit this year; and likely an $800B deficit next year (since some of the spending is in 2010). Thus our debt will grow to $11.5T
And by next year even if the stimulus adds nothing to the economy, we can expect GDP to begin trickling back up (likely 0.5% growth) to $14.2T.
Thus we hit 81% at the end of 2010. Of course if the stimulus works at even a dollar for dollar fashion (using the most conservative estimates), GDP will actually bounce to $15T. That puts the debt at 76.7%.
Worrisome, yes. But it can be handled. We're going to have to end the war in Iraq for financial reasons. It won't be sustainable after 2010. We're going to have to roll back some of the tax cuts in order to raise revenues (see that Presidential chart).
And as we grow economically and our deficits shrink back down, the debt ratio should fall back to its "standard" 60%.