Colorado Senator Mark Udall is persistent by nature. He's a mountain climber who has scaled some of the world's most daunting peaks, from Mount McKinley in Alaska to Mount Aconcagua in the Andes. That dogged pursuit has served him well in his recent career spent navigating the perilous cliffs of Washington's Capitol Hill. And now he has at least one more mountain to climb — the seemingly intractable extension of the Production Tax Credit (PTC), the wind industry's defining subsidy and the financial tool that has helped his rugged home state become a leader in wind energy generation and wind manufacturing.