The lawsuit was filed in federal court Friday. It alleges that Coffman violated federal election law in two ways.
First, the suit says Coffman has removed the names of about 3,000 voters because election notices that were sent to them were returned as undeliverable. That's allowed under Colorado law but the Advancement Project and other groups say that violates federal law.
They also believe that tens of thousands of voters have been wrongly removed within 90 days of Election Day for reasons that aren't clear.
Coffman says he believes he has fully complied with all laws on voter registration and cancellations.
(Copyright 2008 by The Associated Press. All Rights Reserved.)