Semantics

In the context of Giuliani's presidential campaign, Ross Douthat discusses what it means to be a "front-runner":

Obviously, it's a bit peculiar to suggest that the person who's leading in the polls isn't, by definition, the person most likely to win - but in a case where two-thirds of GOP voters still don't know where Rudy stands on abortion, and where McCain is still the betting favorite by a substantial margin, I think it's a reasonable suggestion.

Mr. Douthat is too kind. John Podhoretz has characterized Mr. Giuliani as the "front-runner" because of his lead over John McCain in early polls, though he admits they "may be meaningless". But why not, instead of speculating about this uselessness, follow Mr. Douthat's example and look at the market data?

This answers the question. The polling data are available to the market makers, who nevertheless maintain Mr. McCain as the clear favorite. Unlike pundits, the traders have an incentive to be right. Calling Mr. Giuliani the front-runner is simply willful ignorance of obvious data.