(Bloomberg) -- A ballot measure that could curb oil and gas development in Colorado has attracted attention from some heavyweight names, with Alphabet Inc. co-founder Sergey Brin’s foundation lending support and former Denver Broncos quarterback John Elway opposing it.

Proposition 112 would require new drilling sites, processing plants and gathering lines to be located at least 2,500 feet away from homes, schools and other “vulnerable” areas. That could lead to about 54 percent of state land becoming inaccessible to producers for new oil and gas development, according to the Colorado Oil & Gas Conservation Commission.

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“Polling continues to move in the industry’s direction, with generally ‘yes’ in the low 40s and ‘no’ in the high 40s. Some recent polls seem to be even better, presumably due to the ‘Elway bump’” according to SunTrust, as the Denver Broncos’ two-time Super Bowl champion quarterback and current president of football operations/general manager John Elway appeared in ads recommending people vote no.

Colorado House Majority Leader KC Becker, a Democrat representing a north-central district that includes part of Boulder County, recently said proponents simply don’t have the funding necessary to go up against the oil and gas industry, which has pumped more than $30 million into a campaign to defeat the measure. Proponents, meanwhile, have raised $700,000.

Backers of proposition 112 raised $368,000 for the period of October 11-24, of which only $177,000 was in cash, SunTrust Robinson Humphrey analyst Welles Fitzpatrick said in a note to clients, citing TRACER data. Brin’s foundation donated $170k of “in kind” digital media, he said.

“There has been no other contribution from the foundation, so it is hard to know the real dedication. It’s a little odd, in our opinion, for a large money donor to come in this late with an ‘in kind’ donation, especially from a billionaire with the type of pocketbook that could trump even the industry,” Fitzpatrick said.

Credit Suisse sees the result as likely to be a close call.

“While Election Day’s outcome is ultimately binary, even #112’s defeat could support perception of continued regulatory overhang,” the bank’s analysts led by Betty Jiang told clients in a note.

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