A grassroots campaign to save NBC’s “Chuck” has hit upon a pretty brilliant idea — shower the show’s advertisers with business. Specifically: Subway, which is a major product-placement sponsor of the show.

The campaign, which started on Facebook, asks “Chuck” fans to show their support by buying a $5 footlong Subway sandwich on Monday, the day of the season finale. And to drop notes in Subway feedback boxes pointing out that they spent their hard-earned cash to support “Chuck.”

That could be a pretty smart strategy. And much less annoying than mailing nuts, as “Jericho” fans did to CBS a couple of years ago. In an economic climate that has businesses drooling over anything that will stem the fiscal bleeding, show them that advertising still works. And by showing that direct effect on the ol’ corporate pocketbook, NBC — and advertisers — might just realize there’s more money to be made by continuing the show. Because when you get down to it, bottom line, the networks don’t care a bit about what the fanboys want — they go with what will make them money.

Will it work? Who knows. Call me cynical, but probably not. Still, it’s nice to see fans take such an active role. I might even walk across the street and buy a Subway sandwich on general principle, even though I haven’t watched “Chuck” since last season.

It’s sad that it always seems to be the shows with a small group of diehard fans that get canceled first. And yet “According to Jim” survives, like a cockroach after the apocalypse. Life’s just not fair.