If any U.S. senator ever deserved the term "maverick" it might actually be Rand Paul, not his colleague from Arizona. Another term that indisputably applies to the Tea Party Republican is "leader."
Most junior senators make it to the U.S. Senate chamber for the first time and lie low, often for years, and go along with the party's agenda for the most part, build up some political capital, and then start to influence the process.