Jay Cost, an election-statistics whiz, doesn’t think trendy models predicting election outcomes are worth much. He contends that “all these models seem to share a similar problem: They take the blowout elections of 1952, 1956, 1964, 1972, 1980, and 1984 not as historical peculiarities with little relevance to today, but as central tendencies.” This is nonsense on stilts.

Cost explains:

Today the party coalitions are much more stable, and the battle is fought almost entirely between the 45-yard lines of the field. We have not seen anybody win less than 45 percent in terms of two-party presidential vote in twenty years, and it has only happened once in the House vote (to the GOP in 2008). This means that both sides have secured a solid base of 45 percent, and the range from cycle-to-cycle in terms of two-party vote share is now half of what it once was: the average difference in two-party vote share from 1948 through 1984 was 10.9 percent; since 1988 it has only been 5.8 percent. What’s more, between 2000 and 2008 a total of 10 states voted Republican and Democratic for president at least once, but between 1964 and 1972 forty-three states voted for both sides at least once.

Cost cautions that these models “usually fail to account for the fact that there were simply more gettable voters for Ike in 1956, LBJ in 1964, Nixon in 1972, or even Reagan in 1984. They assume that a president today can still win 60 percent of the two-party vote — even though this was a regular occurrence before 1988 but has never happened since. And it has not happened since because the two parties have finally, after years of struggle and back-and-forth, locked down roughly 45 percent apiece.”

For those who have been around politics for a few decades, the implications of this are clear. As Al Cardenas told me in an interview yesterday, we are talking about a small segment of the electorate who will break very late in the race.

It may be maddening to political junkies that the most important voters, as Cost puts it, are “at the least fickle and at the worst maddening.” Political novices may hang on to every poll, concluding that swings in the results are indicative of something long-lasting, when in fact these are more evidence that public opinion is volatile and that the most critical voters are expressing fleeting reactions, not firm convictions about the candidates.