This paper tests Jacobson and Kernell's strategic decision-making theory by examining individual candidacy decisions in four congressional elections. The partisan balance in a district appears to be an important variable for predicting what type of challenger runs in either an open-seat or an incumbent election. The candidacy decisions of experienced challengers in incumbent elections appear to be influenced by changes in economic conditions, as predicted by the strategic decision-making theory. However, economic conditions do not appear to influence candidacy decisions in open-seat elections. This difference is probably a result of the differing prospects for challenger success in incumbent and open-seat elections. Jacobson and Kernell (1981) propose that the candidacy decisions of challengers are an important link between changes in economic conditions and the electoral fortunes of the party in power (the president's party). Their theory rests on various assumptions about the behavior of quality (i.e., politically experienced, office-holding) challengers in congressional elections. This essay examines these assumptions and subjects them to an empirical test. In Jacobson and Kernell's strategic decision-making model, congressional challengers believe voters hold candidates from the party in power responsible for changes in the state of the nation since the last election. Candidates assume that these evaluations influence the way people vote: if conditions have improved since the last election, voters are more likely to vote for candidates from the party in power; if conditions have gotten worse, then more people will vote for candidates from the party out of power. A challenger is more likely to run for Congress when conditions favor his party, because he thinks his chances of winning the election are higher than they would otherwise be. Conversely, if a party faces an unfavorable political climate and expects strong electoral opposition, candidates from the party will tend to be politically inexperienced, run underfinanced campaigns, and receive fewer votes. The overall effect of individual strategic decisions is to increase the aggregate vote for the party that is advantaged by changes in national conditions and to decrease the vote for the disadvantaged party. A president