'Republican' - The name of an American political party. 'Primary' - The first vote in a series of votes. 'Voter' - a person who votes. An elector. It could be rewritten as 'Republican party members who are voting(or possibly eligible to vote) in the primary election'. 'Tough talking' - this is somewhat idiomatic. It means speaking in a forceful way.

The first refers to people who vote in the Republican primaries, a type of election in the US that helps to narrow down the candidates who will actually run in an election. There are multiple people who want to run for President for the Republican Party so the Republican primaries is an election to choose who will represent the Republican Party in the next presidential election. Talking tough means to talk in a way that makes you appear more intimidating, dangerous, uncompromising, etc. In politics, there can be the implication that the person talking is expressing an unpopular opinion, but one that the speaker feels is correct.