The bottom line is that Boston fears scared Republicans won’t vote and Chicago fears confident Democrats won’t vote. And so, in this final stretch, Boston wants Republicans confident and Chicago wants Democrats scared. Keep that in mind as you read the spin.
In an patent race, the firm that is just about to pass the point where it wins the race and gets a patent has an incentive to slack off a bit and coast to victory. The competitor who is almost toast has an incentive to slack off as he has little chance of winning. But if the race is close, all firms work hard.
Elections are similar except the campaigns have the information about whether the campaign is close or not and the voters exert the costly effort of voting. Campaigns have an incentive to lie to maximize turnout so the team that’s ahead pretends not to be far ahead and the team that’s behind pretends the race is very close. As Klein says, no-one can believe their spin and no information can be credibly transmitted.
If they really want to influence the election, the campaigns have to take a costly action to attain credibility. For example, they can release internal polling. This gives their statements credibility at the cost of giving their opponent their internal polling data.