In recent years Republicans who have failed to toe the party

In recent years, Republicans who have failed to toe the party line have switched to the Democratic Party have dominated leadership positions in Congress. have most often been the most extremely conservative members of the party. have defeated many RINOs. have faced serious challenges in the Republican primary.

Solution

The correct choice is :- Have faced serious challenges in the Republican primary

Explanation:- Republicans in Congress know that if they do not toe the ideological line, they will face opposition in Republican primary elections.