Disclaimer. Don't rely on these old notes in lieu of reading the literature, but they can jog your memory. As a grad student long ago, my peers and I collaborated to write and exchange summaries of political science research. I posted them to a wiki-style website. "Wikisum" is now dead but archived here. I cannot vouch for these notes' accuracy, nor can I say who wrote them.
Leyden and Borrelli. 1995. The effect of state economic conditions on gubernatorial elections: Does unified government make a . Political Research Quarterly 48 (June): 275-290.
Leyden and Borrelli contribute to the developing literature on gubernatorial elections by asking whether united government affects whether governors are held accountable for state economic performance. Previous studies have had mixed findings about the effects of state economic performance, with many finding that it does not influence gubernatorial approval. Leyden and Borrelli find that divided government matters; only when the legislative and executive branches are controlled by the same party does state economic performance matter.
The authors examine 215 gubernatorial elections, drawn from 43 states from 1972-1991. Controls include the national economy (which does matter, conditional on whether the president belongs to the governor's party), whether an incumbent governor is seeking reelection, and so on. Like Peltzman, the authors use first-differencing of economic variables; state economic performance is measured as the annual change in the state unemployment rate.
It's curious that the authors do not include a lag of the dependent variable. If you wish to predict the incumbent party's vote share in gubernatorial elections, you ought to control for how much that party won last time. Their "state partisanship" measure probably helps account for this, but incompletely.
I also wonder whether they ought to have included a dummy for the South, which was a one-party region for much of the period under analysis. They did end up including dummies for certain elections in a couple southern states, but not a dummy for the entire southern effect.
Research on similar subjects