PHOENIX -- Wednesday was a star-studded day in the Arizona Senate race.
It started when Oscar winning actor and environmental activist Robert Redford sent a letter asking donors to give money to Democrat Richard Carmona.
In the letter, Redford says Carmona's Republican opponent, Jeff Flake, threatens the drinking water of 25 million people because he supports uranium mining in northern Arizona.
"Just recently, Rich's opponent called for opening the Grand Canyon and its watershed to uranium mining -- he called the watershed 'prime mining lands,'" Redford says in the letter.
Carmona has made an issue of Flake's support for mining the area known as the Arizona Strip between the Grand Canyon and Utah.
Carmona's talked about it on the stump and his supporters have run ads highlighting Flake's position.
Flake, a former lobbyist for the mining industry, said mining the area would bring jobs to the region and would not harm the environment or the Grand Canyon.
Not to be out done by Carmona, Flake rolled out a new video featuring Republican Presidential nominee Mitt Romney.
So far Romney has cut very few ads for Republican candidates across the county. This underscores how important the Arizona Senate race has become over the past six weeks.
Once thought to be an easy GOP win, Carmona has made it a tight race, one that could tip the balance of power in the U.S. Senate.
In the 30-second spot, Romney urges voters to back Flake because, "he'll get America back on track."