Image caption Customers at Ma and Pa's diner are the bedrock of Mitt Romney's support

Ma and Pa's Diner in Virginia is in a squat building by the highway - a place close enough to the airport to make it an anonymous hangout for travelling types. But it's actually a neighbourhood joint.

The counter is wooden; the jukebox is broken. There are five or six tables in booths, around the same number along the window.

A precariously perched stereo plays a succession of country hits, interspersed with apocalyptic political advertisements that nobody pays attention to.

The customers are white, grizzled, wearing denim and driving old pick-ups and mid-range cars.

They eat the "He-Man breakfast" and drink the coffee out of the not-quite-white mugs.

The waitress sways around the place with the coffee jug. When people come in, they say hello to their friends before sliding onto chairs and concentrating on breakfast.

Romney's problem

The same people were at the Romney rally - sorry, the "Victory Rally" - later in the day, half-an-hour down the road.

Baseball caps, shapeless sweatshirts stretched over bodies that had seen many diner meals, trainers, some check shirts and suspenders. People who didn't worry too much about how it looked before they put it on.

We're not dumb. We can do the math Whit Ayres, Resurgent Republic strategist

A colleague sneered that they were all small businessmen - not true. Jeans outnumbered chinos by a large margin. When the call went up for military veterans to raise their hands, the air was forested with arms.

These are good people, conservative, hardworking, rather baffled by the direction that America and the world have taken. They might as well live in another country as far as New York or Los Angeles is concerned. They'd probably be happy to.

They are the bedrock of Mitt Romney's support. And they are his problem. Because there aren't enough of them. And there are too many of them.

In an audience of maybe 2,000 I saw one black American, planted neatly in the TV wideshot in a grotesquely clumsy piece of photo-cynicism. This in a state that is 20% African-American.

Maybe it is a bit much to ask of a Republican running against an African-American president to have many black supporters. But the complete lack of any diversity in Mitt Romney's rallies should be profoundly disturbing for the Republicans.

There are too many old, white Americans amongst Republican ranks; angry and activist, they shape Republican policy, making much of it deeply unappetising for many of the young, for the college-educated, for Hispanics and for African-Americans.

Fast changing electorate

The New York Times' conservative columnist David Brooks caught it perfectly during the primaries earlier in the year when he wrote of the Republican party as "the receding roar of white America as it pines for a way of life that will never return".

At the same time, there are not enough old, white Americans in Republican ranks, because there are not enough old, white Americans in America, because the electorate has changed and is changing at an astonishing rate, and relying on those white votes will no longer do.

By 2030, one in five Americans will be Hispanic, up from just over one in 10 today.

Steve Schmidt, John McCain's senior strategist in 2008, is quoted in Thursday's Wall Street Journal talking about the "collapse of support for Republican candidates by the fastest growing demographic group in the country"

Eight years ago, he says, Republicans were talking about getting 50% of the Hispanic vote. Now, "we're worried about whether we're going to get 30% nationally".

Some Republicans get this.

"We're not dumb," strategist and pollster Whit Ayres of Resurgent Republic told me. "We can do the math."

Maybe the Republicans can win this time around without much of the Hispanic vote.

But if they want to win nationally in 2016, and want to keep hold of Texas and Arizona and the like, they will have to change.

However good the "He-Man breakfast" is, this will be the last time they can rely solely on the votes from Ma and Pa's diner.