Past research of the effects of campaign spending in Congressional elections has found, contrary to expectations, that incumbent spending lowers votes he or she receives. The authors' model simultaneously determines votes and spending and eliminates this anomaly. A measure comparing the incumbent's voting record to constituent preferences aids model identification. Using two-stage least squares, they find that both incumbent and challenger spending are significant determinants of the popular vote received. Tenure and spending appear to have diminishing returns, and voters appear to punish incumbents who vote against their wishes. Copyright 1991 by Oxford University Press.