Members of the House of Representatives serve two-year terms and are considered for reelection every even year. Senators however, serve six-year terms and elections to the Senate are staggered over even years so that only about 1/3 of the Senate is up for reelection during any election.
Answer: Members of the House of Representatives serve two-year terms and exist thought-out for reelection every even year. Senators still, do six-year terms and elections to the Senate subsist shock over even years because only about 1/3 of the Senate is up for reelection during any election.