Several prominent Republicans are trying to push immigration restrictionist groups to the fringe of the debate by challenging their conservative credentials and attacking their stance on population control, The Washington Post reports. GOP heavyweights like Florida Sen. Marco Rubio and power broker Grover Norquist are backing an effort to inform conservatives about the history of groups like the Federation for American Immigration Reform (FAIR), NumbersUSA and the Center for Immigration Studies (CIS). (SNIP) Those organizations are now the leading conservative voices against immigration, both legal and illegal, and have received the endorsement of Republicans like Senators Lamar Smith (R-Texas) and...