"We had heard horror stories, and people were being sent onerous things," lead organizer Ron Wilcox said.
It lost several thousand dollars from potential donors willing to give only to a qualified nonprofit. That meant fewer funds for recruitment and advertising.
Now, I disagree with these groups on close to everything. And the IRS is totally justified in closely scrutinizing tea party groups - or anyone else - to make sure they deserve to be tax-exempt. A 501(c)(4) can't engage primarily in partisan politics or electioneering.
But the IRS sinned badly by rigging the deck so that conservative groups were more likely to be singled out for questioning. The IRS says it was accidental but concedes it was "absolutely inappropriate."
"To me, it doesn't matter whether you're left, right, center or independent, you do not want the IRS to be used as a political weapon against organizations," said Larry Nordvig, executive director of the Richmond (Va.) Tea Party, which says it was targeted.
At least five of more than 40 tea party groups in Virginia reported being subjected to suspiciously aggressive treatment by the IRS. That created a "chilling effect" that discouraged others from seeking tax-exempt benefits.
The Manassas and Richmond tea parties are among 25 organizations nationwide suing the IRS.
It doesn't seem to have been a big problem in Maryland. That's partly because the state is more liberal, so it has fewer tea party groups. Also, the dominant group in the movement there is Americans for Prosperity, which obtained its tax-exempt status before the IRS targeting began.
The Richmond Tea Party has released a copy of a letter it received from the IRS asking 55 detailed questions about its activities and seeking a response within two weeks. The Manassas Tea Party hasn't released such a letter, but Arnold described similar questions.
"The IRS was requiring that we list every volunteer we had, what they worked on, and how many hours," Arnold said. "We had tons of volunteers working on all kinds of things. Obviously it was intrusive."
The IRS controversy may offer the tea party a silver lining. Both the Manassas and Richmond groups said the publicity has boosted membership.
A more important silver lining is the reminder of the need for public vigilance to ensure the IRS and similar agencies stay rigorously neutral in politics.
McCartney is a columnist for the Washington Post.