Conversation so far:
What is the majority whip?
National Journal described that position as typically requiring a lot of arm-twisting.
Why does it require arm twisting?
CANNOTANSWER.
Is there anything else noteable about the majoriy whip?
Later in 2000, the majority leader of the House, Mike Fasano, promoted Rubio to be one of two majority whips.
Who was the other one?
CANNOTANSWER.
Are there any other interesting aspects about this article?
According to National Journal, during this period Rubio did not entirely adhere to doctrinaire conservative principles.

Question: Why did they think that?
Self-contained rewrite: Why did the National Journal think that Marco Rubio did not entirely adhere to doctrinaire conservative principles?