WASHINGTON — They call her "President Snowe" in the blogosphere. Maine Sen. Olympia Snowe is the only Republican in Congress who might vote for President Barack Obama's effort to overhaul health care and extend coverage to those who lack it. And that gives the unassuming, 62-year-old lawmaker almost as much power over the bill's fate – and that of the millions of Americans it would affect – as the big guy himself. Which is why Snowe's cell phone has lit up with a particular phone number at odd times over the past year, once on the Maine coast as she and her husband drove past a field near their home at Hancock Point. Stopped at the side of the road, she answered – and whatever the leader of the free world was saying to her was lost in the roar of farm machinery cutting hay nearby. "It was classic, different worlds" colliding, Snowe recalls with a chuckle. It's the story of her life these days. Snowe stands as the woman with the most clout in Washington, poised at the intersection of ambitious efforts to change the nation's system of medical care amid competing political forces.