This variation allows us to examine the effect of polling on elections. As Denter and Sisak suggest, polling, by removing some uncertainty about a race, tends to firm up the race in favor of the frontrunner and generally results in a reduction of campaign expenditures and competitiveness. From their abstract:
Under a simple majority rule, there always exist equilibria in which the initially more popular candidate invests more in the campaign and thereby increases his lead in expectation. In other words, polls create momentum for the favorite. Only when campaigning is very effective and the race is very close, a second type of equilibrium may exist: in these situations the trailing candidate also has an incentive to out-spend and overtake the leading candidate. Regardless of the type of equilibrium, polls have a tendency to decrease expected total campaigning expenditures by amplifying ex-ante asymmetries between candidates and thus defusing competition.