With three Colorado cities approving bans or moratoriums on hydraulic fracturing, known as fracking, the natural gas industry is being forced to re-examine its political strategy after a period of explosive growth and broad backing.

Voters in Boulder, Fort Collins and Lafayette approved antifracking initiatives by wide margins on Tuesday, ignoring an industry campaign against the measures that cost at least $875,000. A fourth city, Broomfield, narrowly defeated a proposal for a five-year moratorium on drilling that uses hydraulic fracturing.

More than 100 municipalities have approved similar measures, according to a nonprofit industry monitor, FracTracker, and political opposition to fracking has grown in some areas, like Pennsylvania, where drilling has boomed. But experts say the Colorado votes have added significance because the state has long been a major oil and gas producer and a place where drilling has been both common and tolerated.

Hydraulic fracturing has had bipartisan political support at the highest levels in Colorado, including from its governor, John W. Hickenlooper, a Democrat and former geologist.