If you want to understand why voters no longer trust pollsters, look no further than the latest CNN poll of Ohio voters, showing President Barack Obama with a 50%-47% lead over Gov. Mitt Romney–a result that is within the poll’s 3.5% margin of error, but which suggests a slight Obama lead. The internal numbers reveal that Romney is leading among independents by 2%, and winning Election Day voters by a staggering 13%.

The lead for Obama is based entirely on the poll’s survey of those Ohioans who say they have voted early, or who are likely to vote early.

The hard numbers behind early voting, however–independent from the CNN poll–suggest that Republicans are doing far better than they were in 2008, and that Democrats are lagging significantly in stronghold areas. Turnout models from Gallup and Rasmussen also favor the GOP.

When CNN includes third party candidates, both major candidates drop: Obama still leads by 3%, but at 47%-44%. CNN is projecting that libertarian Gary Johnson will win 5% of the vote, and that Green Party candidate Jill Stein will take 1%. Both of those numbers seem high.

But what stands out most of all is the 13% lead that Romney enjoys among those who plan to vote on Tuesday–and there are many more of those voters.

Does Obama’s wide lead among early and absentee voters cancel out Romney’s huge advantage among Election Day voters? CNN’s poll seems to suggest that it does.

Yet the way the question is framed may sweep in many people who may not, in fact, vote. (The deadline for requesting an absentee ballot is Saturday, and early voting ends Monday.) The poll’s screen of likely voters is weak, including 86% of registered voters.

CNN’s partisan sample is D+2–not terrible, but possibly well below the R+1 to R+3 that may turn up on Tuesday, according to Gallup and Rasmussen.

For months, samples have favored Democrats; they have even been changed to favor Democrats; and yet the race is tied.

That is why the Obama campaign is closing with negative attacks. That is why Republicans are confident, and telling each other to ignore the polls and vote.