The crossword solutions for the term 'REP's COUNTERPART' are SEN and DEM, which are abbreviations for the two major political parties in the United States: the Republican Party (REP) and the Democratic Party (DEM). The Republican Party is generally considered to be more conservative, while the Democratic Party is generally considered to be more liberal. The two parties have been in competition since the early 19th century, and their differences in ideology have been a major factor in American politics ever since.