Complex sentence: In August 2013, Rosen announced that he would seek the Republican nomination for Maine's 2nd congressional district in 2014 to replace Mike Michaud, who is running for Governor.
Split into simpler sentences: In August 2013, Rosen announced that he would seek the Republican nomination for Maine's 2nd congressional district in 2014. He will seek to replace Mike Michaud, who is running for Governor.