Complex sentence: He was then Attorney General of Washington from 1969 until he entered the United States Senate in 1981, defeating longtime incumbent and state legend Warren Magnuson on Ronald Reagan's coattails and an "it's time for a change" ad campaign.
Split into simpler sentences: He was then Attorney General of Washington from 1969 until he entered the United States Senate in 1981. In 1980 he defeated longtime incumbent U.S. Senator and state legend Warren Magnuson on Ronald Reagan's coattails and an "it's time for a change" ad campaign.