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BREAKING: Trump trial day 7 set to begin with testimony from former National Enquirer editor David Pecker

The Agenda: Immigration reform ignites latest battle in GOP civil war

Cracks deepen within the Republican Party--this time over a controversial bill designed to overhaul the nation's broken immigration system.

Cracks deepen within the Republican Party--this time over a controversial bill designed to overhaul the nation's broken immigration system.

The Heritage Foundation released a new report on Monday warning that the latest bipartisan immigration measure would cost an astronomical $6.3 trillion. But in an immigration hearing Tuesday, anti-tax conservative Grover Norquist criticized the study, calling the numbers flawed.

Norquist wasn't alone. Republican Sen. Jeff Flake ripped the conservative think tank's report, as did former Mississippi Gov. Haley Barbour, who wasn't pulling any punches on Twitter:

The @heritage #immigration study is misleading & designed for headlines. The study isn't a serious analysis for good policy. @bpc_bipartisan— Haley Barbour (@HaleyBarbour) May 6, 2013

What's behind the conservative split on immigration reform? Simple strategy, said Talking Points Memo Sahil Kapur on MNSBC Tuesday.

"The Republican Party is worried about this, the strategists who are thinking about the party's long-term viability, and presidential hopefuls, like Marco Rubio and Paul Ryan, who want to support this bill," said Kapur on Tuesday. "What you're seeing now is the extent to which immigration reform is such a fragile effort, with the potential of blowing up into an all-out civil war within the Republican Party."

Watch host Thomas Roberts discuss immigration reform with Tuesday's agenda panel:  Talking Points Memo's Sahil Kapur, Mother Jones' David Corn, and Maria Teresa Kumar, president and CEO of Voto Latino.