Contrary to popular belief, Bremen Democrat TOM MURPHY didn't watch from his crib as Sherman set fire to Atlanta. It just seems like it. First elected in 1961, Murphy's been around long enough to see the bad ol' days of poll taxes and preside (quietly) over the changing of the state flag. Age, though, hasn't blunted the power of the longest serving state House speaker in the nation or how he wields that power. Murphy, 79, has been able to hold on while balancing the demands of the chamber's black caucus and its good ol' boy network. Yet nothing gets done in the House without his blessing. That says something about the political shrewdness he's honed in his four decades in office, a shrewdness, House Democrats say, characterized by an ability to make you think he's building consensus.