LCV made the same claim last week in a $400,000 ad buy, which marked the group’s entry into the race.
Andrew Wilder, spokesman with the Flake campaign, told The Hill on Friday that research shows “responsible mining” in that area would pose no risk to the Colorado River, citing a study by the Arizona Geological Survey.
“Richard Carmona and his liberal patrons can try to deceive Arizonans about Jeff Flake's record of supporting economic development in the Arizona Strip, but they simply do not have science on their side,” he said.
Carmona, the former U.S. surgeon general, has been gaining in the polls after failing to gain much traction through most of the campaign.
“This has become a truly competitive race. We have the chance with Rich Carmona to elect a real ally to the Senate,” Jeff Gohringer, LCV spokesman, told The Hill.
RealClearPolitics, a website that aggregates polling data, shows Flake with a 0.7 percentage point lead.
The Hill rates the race as a toss-up.