Jenny Beth Martin, the co-founder of Tea Party Patriots, has filed an ethics complaint with the Senate Ethics Committee against the majority leader, charging him of "unlawfully and unethically targeting private citizens."
Reid, it says, has "misused Senate staff or resources to engage in partisan campaign activity in violation of federal laws and Senate rules."
The Nevada Democrat has focused much of his election-year fire on the billionaire brothers, whose Americans For Prosperity has pledged to spend $125 million for the midterm elections and who are, for liberals the symbol of the extreme influence of big money in politics.
"Senator Reid opposes and has spearheaded a sprawling campaign of attacks against Charles and David Koch -- two private citizens who are running for no elected office -- and those he perceives as their supporters," the complaint reads.
It accuses him of violating campaign finance laws that prohibit using congressional space or on-the-clock staff for political purposes, and of violating the Senate ethics manual's code of conduct, among other no-nos.
Reid, has in turn, accused the Kochs of several violations of their own, including the Foreign Corrupt Practices Act, and a spokesman for the majority leader dismissed the complaint as a stunt.
"We are shocked -- shocked! -- that a publicity-seeking, extremist tea party group which has received hundreds of thousands of dollars from the Koch brothers' secret bank would attempt a frivolous publicity stunt to distract from the Kochs' efforts to rig the system for billionaires like themselves," said Adam Jentleson, in a statement.
"The shadowy, billionaire Koch brothers are pulling out all the stops to get Senator Reid to stop shining a light on their efforts to buy our democracy, but he will not be silenced," he said.