Rep. Bachmann released a letter that Mr. Gingrich signed in 2004 supporting a proposal by President Bush for a guest-worker program that would have given undocumented workers employee benefits.
Rep. Bachmann called Mr. Gingrich “the most liberal G.O.P. candidate on the issue of immigration reform.”
The issue arose after a debate on Tuesday night in which Mr. Gingrich called for a “humane” solution for illegal immigrants.
Republican primary voters disapprove of any program suggesting amnesty for illegal immigrants.
On Wednesday, Mr. Romney attacked Mr. Gingrich for tying legal status to the time someone has been in the country. “How about someone who has been here 20 years?” he said. “How about 12 years? How about 10? 5? 3?” He, too, labeled Mr. Gingrich’s proposal “amnesty.”
Mr. Gingrich said Friday at a campaign appearance that his Republican rivals were twisting his position. He repeated his support for a system to give legal status to some who have long been in the U.S., stating the least would be twenty-five years. He would leave the choice to grant legal status to local community boards.
Mr. Gingrich said he would secure the Mexican border by January 1, 2014 and fine businesses that hired undocumented workers, but in suggesting anything less than deporting all 11 million illegal immigrants, he opens himself up to charges of “amnesty.’’
Rep. Bachmann, who has made a hard line on illegal immigration a signature of her campaign, repeated that Mr. Gingrich favors amnesty for all 11 million.
The February 2004 letter that she circulated, printed in The Wall Street Journal, was an indication of how conservative opinion has shifted on the issue. Among its signatories was Ed Goeas, who earlier this year was an adviser to Mrs. Bachmann.