"Thirty years of voluntary separation from the state I love has been enough," Mark Hatfield said Friday, announcing that he would not run again next year for the United States Senate. The 73-year-old senior Senator from Oregon said that personal concerns rather than political ones are behind his decision not to seek a sixth term. "The Senate is losing one of its very best," said Senator Robert Byrd of Hatfield, who had honed a reputation as a maverick moderate during his long legislative career. "Hatfield's departure, added to the departure announcements of people like Sam Nunn, Bill Bradley and Nancy Kassebaum, follow a pattern," says TIME's Laurence Barrett. "And that pattern is that the ideological center of the Senate is leaving. While it is important to know who will replace him, it is apparent that Congress is becoming more polarized. This Congress is more polarized than the last one, just as that one was more polarized than the one before. The moderates of both parties are resigning." Barrett also notes that the other Oregon Senate seat, now vacant after his September resignation, was also held by a GOP moderate, Senator Bob Packwood.