Complex sentence: Frey was not a candidate for reelection to the Ninety-sixth Congress in 1978, instead choosing to launch an unsuccessful run as a candidate for the Republican nomination for governor, having lost to Jack Eckerd, whom Kirk had beaten for the nomination in 1970.
Split into simpler sentences: Frey was not a candidate for reelection to the Ninety-sixth Congress in 1978. Instead he launched an unsuccessful bid for the Republican nomination for governor, having lost to Jack Eckerd, whom Kirk had beaten for the nomination in 1970.