There’s an unwritten rule in the world of money and politics: the smaller the audience, the bigger the role of money in determining the outcome. This works both in elections and in legislation. Not many people pay attention to a humdrum House reelection contest, so the challenger can’t get traction and the incumbent’s war chest is usually sufficient to stave off anything but a renegade millionaire.

In legislation, the more attention a bill gathers, the more opponents it tends to pick up and the more expensive its passage is likely to be. Earmarks are the perfect example of stealth legislation – the items are buried in bigger bills and hardly anyone knows about them.

Every once in a while, though, a bill or an issue pops out of its accustomed track and draws the attention of the public at large. When that happens, the dynamics change, things become more expensive, and the outcome is less predictable.

For years, the coal mining industry has been coasting along comfortably in Washington. Its campaign contributions, which spiked heavily through soft money in 2000 and 2002, have been more solidly Republican than almost any other industry – a helpful asset in a town where the GOP controls all three branches of government.

But this past winter’s dramatic coal disasters – involving the death of 33 miners – brought long-dormant mining safety issues into sharp public focus.

When Congress finally revisited mining safety rules this week, even the industry joined in to back tougher rules. The bill passed the House yesterday on a vote of 381-37. It won unanimous approval in the Senate last month.

So far this election cycle, there’s been no big jump in coal mining contributions. Like most industries, its political giving has dropped with the banning of unlimited soft money contributions. But because 33 miners lost their lives – and the whole country noticed – the long-buried issue of mine safety jumped onto center stage and Congress responded to the public’s attention.

To give the industry credit, they didn’t hunker down and try to fight it. (There’s another old political rule: if you can’t beat ‘em, join ‘em.) The safety measures passed yesterday by the House – limited as they were – were clearly a step forward in making life somewhat less dangerous for coal miners.

But it’s a sure bet that if the audience paying attention had been the usual one, it wouldn’t have happened.