I don't doubt the Tea Party folks have been a huge help for Republicans, particularly in House races and lower-ballot places, where voters are less attuned to the details of the various candidates.
But in statewide races, and particularly the Senate, the teabaggers likely cost the GOP the majority.
First, the easy calls -- the GOP would've easily picked up Nevada, Delaware, and Colorado had the establishment candidates won. Nevada was toxic for Reid, who was polling in the 30s at one point. Republican Rep. (and former Gov) Mike Castle was a surefire GOP pickup in Delaware. And Sen. Michael Bennet barely eked out a victory in Colorado against a real nutjob candidate. He'd be toast against a conventional Republican (like Kelly Ayotte in New Hampshire).
Now, those three would've given the GOP a 50-50 Senate, which would still leave Democrats (nominally) in control.
But the teabaggers were even more damaging than that.
Had the GOP nominated Trey Grayson in Kentucky, there would have never been a senate race of note. Grayson led Conway by 20 points in the polls. But by nominating Rand Paul, it forced the NRSC and allied organizations to spend millions to win the race. Rove's outfit and similar groups spent $5-6 million trashing Conway, in addition to several million more from the Republican Party itself. That money could've made the difference in Colorado or Washington.
Had Linda McMahon not muscled former Rep. Rob Simmons out of the race, the GOP would've had a top-tier challenger in Connecticut. Simmons would've still been the underdog, but the Democrats would've had to spend far more money locking down the seat. As is, the Democrats won the seat by just 10 points in this heavily Democratic state against a terribly flawed candidate. (Look at the governor's race, where the Dem will win it by just a sliver.) A solid challenger like Simmons would've been dangerous for Connecticut Dems in this toxic year.
In Florida, the GOP gave up an easy GOP pickup for Marco Rubio, and he cost the NRSC and allied organizations $4-6 million. Again, money that could've been spent expanding the playing field even further.
In Nevada, the NRSC and allied groups spent about $10 million trying to salvage their shitty nominee, to no avail.
Given that the Washington Senate race is coming down to a narrow hold, that fuckton of money wasted on teabagger candidates (both the winners and losers) could've been enough to knock out Patty Murray in Washington, or to drag Ken Buck across the line in Colorado.
So while we can safely assume the teabaggers cost the GOP three Senate seats, chances are they cost the GOP a Senate majority.
