This article from the CATO Institute is a great case to make to fiscal conservatives for why they should vote for Kerry.
A Case for Divided Government
by William Niskanen
William A. Niskanen is chairman of the Cato Institute and former acting chairman of President Reagan's Council of Economic Advisers.
For those of you with a partisan bent, I have some bad news:
Our federal government may work better (less badly) when at least one chamber of Congress is controlled by a party other than the party of the president. The general reason for this is that each party has the opportunity to block the most divisive measures proposed by the other party. Other conditions, of course, also affect political outcomes, but the following types of evidence for this hypothesis are too important to ignore:
Point One. The rate of growth of real (inflation-adjusted) federal spending is usually lower with divided government.
Point Two. The probability that a major reform will last is usually higher with a divided government because the necessity of bipartisan support is more likely to protect the reform against a subsequent change in the majority party.
Point Three. The prospect of a major war is usually higher with a united government, and the current war makes that clear.
http://www.cato.org/dailys/05-07-03.html
Much more detail in the article, I just picked the bullet points up.