What conditions help stable patterns of party support to emerge? Using pooled time-series cross-section data on election results from 15 East European democracies, the empirical analysis finds that (1) right after a regime change electoral volatility increases while the trend is reversed after democracy has endured for about a decade; (2) ethnic cleavages have no effect on stability while social cleavages affect electoral stability only during economic downturns; (3) both institutions and economic performance influence the stability of party support; however, the effect of the latter diminishes over time when democracies mature.