That's the type of nonsense that poli sci profs would tell their students while still high from last night's party. It has no bearing on the real world, however.
Power in the Senate comes from holding the Majority. That's who chairs committees. That's who decides when to bring up "which" legislation and nominations. Moreover, it's the majority Party that decides on the final content of bills during the House-Senate conferences after all but the final voice votes are taken.
Buck the Majority party in the Senate and you lose your plum committee assignments. You lose your Party campaign funding. You lose support for your own legislation and nominations. In short, you lose.
So "power" doesn't come from so-called moderates who buck the Majority Party's Senate leadership.
Although what I say is heavily contingent on a group that fails to organize itself year after year, the nonsense you just spoke is what you'd hear from a Political Science Professor - or from the movie "Dinstinguished Gentleman". It isn't that black and white. If it was we should just move to a system of voting simlar to Britain and just vote straight party line. Would make no difference...