The answer is in the article, which I show above.
Each of us have three representatives. One House; two Senators. We vote house every two years, one Senator comes up 2/3 of the time.
Use those votes (and money if you can) to help the most conservative candidate that has a chance of winning. Primaries are the time to replace unsatisfactory Republicans, if possible.
But holding the majority is powerful, even at the expense of having some so called rinos (I don't like the terminology, because it so abused).
Holding the majority means committee chairmanships. That in turn controls the legislative agenda.
As bad as Specter is regarded, he DID help get Roberts and Alito confirmed. A dem chairman could have EASILY blocked same. Would have.
That is just one example.
And a very good example it is, thanks for the post.