The phrase "contentious race" means a competitive and intense competition or contest where there is a lot of disagreement or conflict between the participants or groups involved. Full definition
Espaillat, who takes over from longtime Rep. Charles Rangel in the 13th Congressional District effective Jan. 1, 2017, ran a series of very contentious races for the seat since becoming the state senator of the 31st District in 2010, before which he served as the assemblyman for the 72nd District since 1996. (dnainfo.com)
This week's issue of New York Magazine examines some of the country's most contentious races in «The Mud Report.» (nymag.com)