Political campaigns are commonly understood as random walks, during which, at any point in time, the level of support for any party or candidate is equally likely to go up or down. Each shift in the polls is then interpreted as the result of some combination of news and campaign strategies. A completely different story of campaigns is the mean reversion model in which the elections are determined by fundamental factors of the economy and partisanship; the role of the campaign is to give voters a chance to reach their predetermined positions. Using a new approach to analyze individual level poll data from recent presidential elections, we find that the fundamentals predict vote intention increasingly well as campaigns progress, which is consistent with the mean reversion model, at least at the time scale of months. We discuss the relevance of this finding to the literature on persuasion and activation effects.