Yes the Tea Party is done in the state of Mississippi
In a state where race in the past has been used to elevate candidates of both parties the Mississippi Tea Party has found that their message of hatred and exclusion doesn't play well to the majority of voters, black or white. In fact it served to motivate black democrats to vote for the specific reason of voting against the Tea Party!
Mcdaniels Barely lost
Mcdaniels barely lost the race, and may challenge the results. If the Tea Party where through then the race would have been much closer. Mississippi is also a very conservative state. The Tea Party message hits home with a lot of its residence. I would not count them out just yet.
Tea Part is not done
The Tea Party is not done in Mississippi. It is a very conservative state and the Tea Party will continue to be attractive to a certain portion of the population there. Overall the Tea Party will remain a force in any state with a strong conservative slant to the electorate.
No, one race isn't a good measure.
The establishment Republicans pulled out every stop to defeat the Tea Party challenger. They only barely succeeded. The Tea Party will likely consider this narrow defeat a demonstration of the political gravitas they can muster without any mainstream support. It should only embolden and reinforce their efforts to unseat the more moderate wing of the Republican party.