In a 2001 letter by Tanton being circulated as part of the current campaign, he laid out his idea to "move the battle lines on the immigration question in our favor" by convincing Republican lawmakers that "massive immigration imperils their political future." The goal, he wrote, was to "change Republicans' perception of immigration so that when they encounter the word 'immigrant,' their reaction is 'Democrat.' " Organizers of the campaign against the groups found the letter at the University of Michigan's Bentley Historical Library, which houses Tanton's papers.
An aide to Tanton, now 78, said Tanton was unable to speak. But the aide, K.C. McAlpin, said Tanton was an "ardent conservationist" who was being targeted in a "sort of McCarthyism game that the far left has been playing and is now being played by some people who call themselves conservatives."
The dispute has prompted some tense encounters in recent days.
When word spread, for instance, that Rubio's staff was bringing Lopez to the Senate aides meeting last week, other Senate offices contacted the three groups, each of which sent a representative.
"It was awkward," said one staffer, speaking on the condition of anonymity to discuss a private meeting. The staffer described the critics' tactics as "over the top," saying the groups have been a "great resource" for data, research and expert testimony.
Another testy moment occurred recently at the weekly conservative strategy session hosted by Norquist when Lopez stood to present his arguments. Hans von Spakovsky, a former Justice Department official in the George W. Bush administration who now works at the conservative Heritage Foundation, spoke up to defend the credibility of the Center for Immigration Studies.
"I haven't heard folks take on the substantive arguments CIS is making and saying why they're wrong," said von Spakovsky, who declined to discuss details of what happened in the off-the-record meeting. "Instead you just get these scurrilous attacks."