Party identification and core political values are central elements in the political belief systems of ordinary citizens. Are these predispositions related to one another? Does party identification influence core political values or are partisan identities grounded in such values? This article draws upon theoretical works on partisan information processing and value-based reasoning to derive competing hypotheses about whether partisanship shapes political values or political values shape partisanship. The hypotheses are tested by using structural equation modeling techniques to estimate dynamic models of attitude stability and constraint with data from the 1992–94–96 National Election Study panel survey. The analyses reveal that partisan identities are more stable than the principles of equal opportunity, limited government, traditional family values, and moral tolerance; party identification constrains equal opportunity, limited government, and moral tolerance; and these political values do not constrain party identification.