The Tea Party Express does seem to be the worst of the vocally active "Tea Party" groups out there (well, I suppose fake "Tea Party" candidates who are really Dems would be worse, but they're not really an organization).
They're a California based group that has a nasty habit of sticking their nose in races elsewhere in the country where they know nothing about the local issues or the candidates, and undermining the local tea party groups who are making genuinely educated endorsements. A perfect example is when the TPX endorsed squishy loser Mark Neumann (who was only polling 10% anyway and had no chance of winning the nomination) in the Wisconsin Senate primary and confused local conservative voters enough to split the Tea Party vote and allow GOP establishment favorite Tommy Thompson to win the nomination.
Elsewhere, they've also endorsed terrible candidates with no conservative track record who have muddied up numerous races where there is a clear proven conservative candidate. Their tactic seems to be to "get behind" any candidate who screams he or she is "ANTI-ESTABLISHMENT!!!" the loudest (giving absolutely no weight to the candidates track record or qualifications for the job) and jump into the race with guns blazing. This also includes if the candidate is as establishment as it gets, but just campaigns as "anti-establishment".
Looking at their past endorsements, I'd say the TPX backs the wrong horse 60-70% of the time. They've endorsed some decent candidates, but a lot of those races were no brainers where the only other candidate was a horrible RINO.
The TPX co-founder (Sal Russo) also has a long track record of being on the amnesty bandwagon. Recently this was exposed and he's now backtracked on the issue. Go figure.
Oh, yeah, that Neumann endorsement. Remember that unhinged TPX’er who lost his $hit when we called out Neumann as a lousy candidate/retread ? Gee whiz, that was fun times.