If Bush is re-elected he pledges to make his upper-bracket tax cuts permanent. That will put the US deeper and deeper in debt, leaving it in a weak position to compete with China and India. Many Republicans don’t want extend Bush’s tax cuts.
The Kerry Budget has its weaknesses too, but it at least it doesn’t continue the fiscal irresponsibility of tax cuts in times of War and Deficit.
(Kerry still gives cuts to the middle class too)