The Romney campaign is joining the ranks of supporters who have decided that major national polls show Romney losing only because the samples are overly weighted with Dems. Romney pollster Neil Newhouse insists that public polling averages are “skewed,” and that the 2012 electorate will not show the same minority and Dem base composition as the 2008 one did.

But in an interview with me, Obama campaign pollster Joel Benenson mocked the idea that the electorate will diverge meaningfully from that of 2008 as as delusional.

“The notion that this electorate isn’t going to be as diverse as it was is frankly a fantasy,” Benenson said.

“The percentage of African Americans has gone up in every presidential election since 1992, except in 2000, where the number went down one percent,” Benenson continued. “Latinos have gone up in every election since 1992. And 18-to-29-year-old voters have been at 17 percent or more in every election since 1992, except 2000."

“There are some historical trends that appear to be pretty irreversible,” Benenson said. “That reality may be uncomfortable for the Romney campaign, but this will be an electorate that has been as diverse as the previous four presidential elections.”

Benenson also noted that the electorate has, in fact, tilted Democratic by single digits in a number of recent presidential elections.

Buzzfeed reports that the Romney campaign disputes polls showing Obama leading in Ohio, claiming its internals show the race within the margin of error. Asked to respond, Benenson said: “I’m sure that if the Romney campaign wants to release its internal polls, people would pore over them with great interest."

The Romney campaign has repeatedly pointed to the Gallup tracking poll as evidence that the race is still close. Pressed on the Romney camp’s Gallup argument, Benenson said: “I understand that the Romney campaign feels that they need to talk about the public polls. We don’t.”

The Gallup tracking poll, along with Rasmussen’s, have become central to the case that literally all other polling is skewed against Romney. But Mark Blumenthal has exhaustively demonstrated that Gallup under-represents minorities. Numbers cruncher Nate Cohn bluntly labeled the Gallup poll an “outlier.” And Nate Silver has promised to weigh in on the discrepancy in coming days, so stay tuned for that.