From this:

A new battle has flared inside the Republican Party in recent days as supporters of more-liberal immigration laws wage a behind-the-scenes campaign to discredit the influential advocacy groups that have long powered the GOP's hard-line stance on the issue.

..[pro-amnesty Republicans] are accusing those groups - Numbers USA, the Center for Immigration Studies (CIS), and the Federation for American Immigration Reform (FAIR) – of masquerading as conservative. Critics say the groups and some of their supporters are pressing an un­or­tho­dox agenda of strict population control that also has included backing for abortion, sterilization, and other policies at odds with conservative ideology.

"If these groups can be unmasked, then the bulk of the opposition to immigration reform on the conservative side will wither away," said Alfonso Aguilar, executive director of the Latino Partnership for Conservative Principles and a leading organizer of the effort.

...Conservatives who are taking on the groups, including [Marco Rubio], anti-tax activist Grover Norquist and officials of the Catholic Church, argue that the three organizations are motivated by far different philosophies than many of their Republican allies realize. Among those views: that population growth from increased migration threatens the environment.

...Rubio's aides last week brought one of the organizers of the effort to undermine the groups, Mario H. Lopez, a party strategist on Hispanic politics, to a regular meeting of GOP Senate staffers, where Lopez distributed literature about the groups' backgrounds and connections. Rubio also raised concerns about the groups' leanings during a recent conference call on immigration with conservative activists.

Rubio's spokesman, Alex Conant, said the senator "has argued that some groups that oppose legal immigration should not be considered part of the conservative coalition," adding that the "vast majority of Republicans strongly support legal immigration."

Kevin Appleby, director of immigration policy for the U.S. Conference of Catholic Bishops, said in an e-mail to The Post that "pro-life legislators should think twice about working with these groups, as their underlying goals are inconsistent with a pro-life agenda."

1. Things like this aren't new: during the George W Bush years, Chris Cannon and other amnesty supporters led a highly similar smear campaign.

2. One necessary part of a defense against such smear campaign is a good offense. However, the anti-amnesty groups aren't willing or able to provide such an offense nor assist those who can. For instance, sending people to the Marco Rubio page or using the ideas on that page would be a great way to discredit him to his current or potential supporters. Yet, those groups or their supporters aren't willing to do that. It would be very smart to have a cohesive effort designed to discredit those like Rubio, but the only people who are capable of putting that together aren't willing to do it.

3. For past coverage of others involved, see Grover Norquist, Mario Lopez, Alfonso Aguilar, Kevin Appleby, and US Conference of Catholic Bishops.