Q: Why do small towns beat big cities in presidential elections?

A: They vote.

Okay, it’s more complicated than that, but not MUCH more complicated.

Democrats are inevitably flummoxed by the fact that their politicians often lose, while the Republican candidates favored by rural Americans prevail.

Why should small town folks — who tend to favor personalities like George W. Bush and Sarah Palin — get their way?

It’s a complicated question, but the biggest single answer is…democracy. Yup, it’s that tricky little step in the process called voting.

Rural folks tend to be whiter (a lot whiter) and older (increasingly, a LOT older) than their urban and suburban neighbors.

And since white seniors tend to be the most responsible voters, they wield disproportionate clout.

Let me put it another way.

If you have ten million urbanites, but only three million of them vote, those other seven million citizens are effectively invisible politically.

Doesn’t matter how many protest marches they attend or how many petitions they sign. Without casting a vote, they don’t register.

There are signs that Democratic constituencies in urban America — blacks, Hispanics and young people — are getting better at putting their ballots where their mouths are.

Will it be enough to lift Barack Obama over John McCain?

History says no. Again and again, center-left politicians have tried to rally the under-29 crowd and the Hispanic vote, to no avail.

Obama’s people say technology and his unique appeal will change all that; they also point to higher-than-expected turnout in 2006 and in this year’s primary.

But with Palin on the GOP ticket, my bet is that rural folks will once again get busy and march to the polls in the kind of numbers that put the downtown crowd to shame.