Could you post a link where Lott's uncle said that Lott was a dues paying member of the CCC? That and the refusal to sponser the honor to the three murdered freedom riders are the biggest points I think.
The extension of the application to the south of the voting rights monitoring of the Civil Rights Act (there was no vote regarding extending the Civil Rights Act itself; that has no sunset clause), can be defended I suppose because there may not have been any evidence by then that blacks were still being disenfrancised, or more so in the south than in the north, and thus it was discriminatory, and should be ended or applied nationwide. The merits of that are fact driven arguably, not principle driven.
Again, I caution against weakening a case by overstating it. Your two solid bullet points may well be enough to put a stake in his heart, particularly if it can be substantiated that Lott was a dues paying member of the CCC, and has been lying about it. I fear that one, if true, will cause him to exit from the senate. That one is on a whole different level. I hope it proves to be untrue.
A request for clarification, as I often get my Bob Jones controversies oncfused: was it the tax-exempt status or the eligibility of Bob Jones students for federal financial aid and student loans that Lott supported? Or both?