Michael Castle (Getty)

Delaware Republican Rep. Michael N. Castle ‘s decision to forego consideration for a top-ranking position on a key committee is the latest sign he’s seriously considering retirement or a run for the Senate in lieu of seeking re-election to the House.

Castle was interested in becoming the ranking Republican on the Education and Labor Committee — a post that California Republican Rep. Howard P. “Buck” McKeon is vacating to become the top-ranking Republican on the Armed Services Committee. But Castle said in a statement that he couldn’t commit to Republican leaders that he will run for a tenth term next year in his state’s at-large congressional district.