The Tea Party, like many American protest movements, jumped into the electoral fray quickly.  This is the way our system is set up; frequent elections mean that activists always seem to have the chance to replace politicians they don’t like with someone they do.

And Tea Party candidates have done very well–at least in Republican primaries.  Slate’s David Weigel has been tracking their efforts; his scorecard shows Tea Partiers beating Republican establishment candidates a little more than half the time.

The terrain gets tougher in the general elections–and in governing.  Movement-supported candidates virtually always disappoint their supporters, but in all kinds of different ways.  They lose, they fail, or they change.

They may be lousy candidates, bad at articulating a message and unlikely to win–and carrying personal baggage to boot.  (This seems to be the early consensus on Christine O’Donnell.)  Sharron Angle’s nomination gave Harry Reid an unexpectedly good shot at retaining his seat.  Supporting the purer movement candidate often means electing the opposing party.

And if they win, hold tight to their ideals, they’ll  be ineffective, unable to deliver on anything that matters to their supporters.  The nasty process of politics demands compromise and delivering less than you wanted–or promised.  Again, the system is set up that way.   If Rand Paul follows his father’s model in Congress, he will develop a record of statements that inspire the faithful and no legislative achievements.

Or, they  may win and become, shockingly, effective politicians, making deals and compromising.

The late “liberal lion” of the Senate, Ted Kennedy, constantly took flack from activists for his willingness–and extraordinary facility, in cutting deals, sponsoring legislation with Utah’s Orrin Hatch, and coordinating with President George W. Bush on No Child Left Behind.  The resulting legislation was always so much less than liberal supporters wanted–but there was resulting legislation.

Actually, there’s no need to go back to Ted.  Isn’t Barack Obama a perfect example of the movement candidate who compromises to try to get things done (e.g., still 50,000 service people in Iraq; no public option for health care)?