Speaking with reporters in Seattle, the seven-term member of Congress said he decided to resign from his seat after watching Republican presidential hopefuls campaigning on what he called a "divisive social issues agenda" and seeing Republicans in the state legislature propose cuts in education spending, The Seattle Times reported.
He conceded the decision was difficult but said it was "very rational."
"But I asked this question: 'Where can I do most good for the state of Washington?'"
The timing of Inslee's resignation has political implications in the state, the newspaper said. If he had resigned before March 6, Gov. Christine Gregoire would have had to order a special election to fill his seat. As matters stand, the seat will remain vacant until voters choose a representative in the November elections.