It is a truism that voluntary voting, particularly where turnouts are low, shifts the campaign emphasis from convincing undecided voters to getting one’s supporters to the polls. However, you have to see it in action to realise how far this can go.

I’m in Denver and the local office of the Obama campaign is buzzing. They have three rounds of volunteer inductions, plus occasional off-the-streeters such as me. The local area co-ordinator is very excited as I walk in.

“We had 177 in the morning group and 200 in the second shift,” he announces to someone who appears to be visiting from another office. “If we get 123 in the last group we’ll hit 500. That’s just amazing.”

I didn’t find out if they hit 500, but amazing it certainly is. This is just one office, albeit the closest to downtown Denver, which is why I am here. There are several others dotted across the city and dozens in smaller towns across Colorado. Quite a few volunteers are arrivals from California, and one individual in the office seems to spend most of his time organising billets for them. He even has a database listing whether hundreds of people who have offered their spare rooms to these out-of-staters have a pet, and if so its species.

There are so many Californians here because Nevada is “full”, they simply can’t handle any more volunteers there apparently, so West Coast offices have told their people to go hundreds of miles further east to assist the campaign.

So what is the campaign doing with all these people? Are they out on the streets offering undecided voters last minute information? Holding up banners? Offering information to voters about to enter the pre-polling centres? Door knocking undecideds for goodness sake? None of the above. On the streets the only sign of active campaigning is two men standing on a busy street corner holding up a banner for Nader. True there are thousands of bumper stickers and window signs for Obama, and a smaller number for Udall, the environmentally minded Democrat candidate for the Senate, but there is no sign of people actually doing anything after they’ve stuck these up.

The deputy local coordinator tells me that somewhere else there are some people contacting Independent voters who might still remain to be convinced, but adds “We’re not doing a lot of that.” So what are they doing with these hordes of volunteers? Having them contact “sporadics”, people who usually vote Democrat, but only turn up once every few elections.

Life must be pretty irritating if you’re a sporadic around now. Apparently most have been contacted three times by phone or in person, and they’ll get hit once or twice more before polls close if they haven’t voted by then. Here then is the explanation for the huge rush of early voters. Sure some are doing it because their boss won’t give them time off work on election day, and others are worried they’ll find themselves struck off the rolls a la Florida 2000 for being excessively black. Voting early gives these people a chance to challenge any wrongful removal, but for huge numbers of Democrats (and presumably Republicans, although the volunteer base there must be smaller) the main reason is that once you can say you’ve actually cast your vote the Obama/Udall campaign (Biden is invisible here) will stop harrassing you.

Could all this pressure create a backlash, causing people to vote against their tormentors? The local deputy thinks this is unlikely, although perhaps she just doesn’t want to admit the possibility all her endless hours could be counterproductive. She’s probably right though, particularly when the people being targetted have no reason to love McCain.

And perhaps it is true that the job of securing the hearts and minds of swinging voters is best left to the candidates themselves, via the media and advertising, where Obama is blitzing McCain here as everywhere is considered in play. But I can’t help feeling just a little uncomfortable at the notion that out there are millions of independents (Colorado is famous for a particularly high proportion of voters refusing to register for a party) who are being largely ignored by possibly the greatest campaign army of all time as it stumps the streets, slowly crossing off names of the faithful once they’ve done their civic duty.