Same-state rivalries abound in the Senate. And delicious tales of clashing egos and epic grudges are widely shared -- doled out by insiders like pieces of Hill Candy. Some of these “special” relationships matter more than others. For years, tensions along the border of Ted Kennedy and John Kerry fascinated Senate-watchers, because both Massachusetts patricians had such sway. Now the complex partnership to watch is the team from Maine. Olympia Snowe and Susan Collins, both moderate Republicans, are wedged into a tight political corner together. As the polarized right and left scream for airtime and dollars, and the middle is vanishing, these two women – often ignored -- have unprecedented power. On Capitol Hill, their nickname is The Sisters. Publicly, the duo is known for voting together. Lockstep. Straight down the middle. They have been the deciding votes on the most monumental legislative battles of our time. In the last fifteen years, they have voted in unison on war, taxes, gays, guns, health care and the stimulus package. And when it came to the 2008 presidential election, they both went early for John McCain. In spite of this congruity, raise their names among staffers, journalists, even other senators, and the first thing mentioned is the wintry chill between them. “Did you say you were writing a dual-profile – or, is that d-u-e-l?” asks Sen. Joe Lieberman with a chuckle. He is a close friend and colleague of Susan Collins. “Oh, I shouldn’t have said that.”