BOSTON (January 5, 2013)--Infighting has penetrated the highest levels of the House Republican leadership and long-standing geographic tensions have increased, pitting endangered Northeastern Republicans against their colleagues from elsewhere in the country.

Enraged tea party leaders are threatening to knock off dozens of Republicans who supported a measure that raised taxes on the nation's highest earners.

The GOP's internal struggles were painfully exposed after Mitt Romney's loss to President Barack Obama on Nov. 6, but they have exploded in recent days and the fallout could extend well beyond the party's ability to win policy battles on Capitol Hill.

It could hamper Republicans as they examine how to regroup and attract new voters after a disheartening election season.