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A.J. Spiker, a close ally of Ron and Rand PaulRandal (Rand) Howard PaulOvernight Defense: Senate confirms Haspel as CIA chief | Trump offers Kim 'protections' if he gives up nukes | Dem amendments target Trump military parade Hillicon Valley: Lawmakers target Chinese tech giants | Dems move to save top cyber post | Trump gets a new CIA chief | Ryan delays election security briefing | Twitter CEO meets lawmakers Overnight Finance: Watchdog weighs probe into handling of Cohen bank records | Immigration fight threatens farm bill | House panel rebukes Trump on ZTE | Trump raises doubts about trade deal with China MORE who became chairman in 2012, has been criticized by many establishment Republicans for pushing his socially conservative, libertarian-leaning ideology on the party and for attempting to move the state party's convention later into the summer.

The Polk County Republican Party, the largest county organization in the state, called for Spiker's resignation on Tuesday night, and other top Republicans including Sen. Chuck GrassleyCharles (Chuck) Ernest GrassleyHow House Republicans scrambled the Russia probe Dem lawmaker spars with own party over prison reform Overnight Energy: Pruitt taps man behind 'lock her up' chant for EPA office | Watchdog to review EPA email policies | Three Republicans join climate caucus MORE (R-Iowa) and Iowa Gov. Terry Branstad (R) were critical of his now-abandoned effort to move the state's convention date.

Spiked fired back with a letter pointing out the state party is in great shape financially and said those who disagree with his leadership "will have their opportunity to make a change when the next election for chairman comes up."

The letter is the latest flare-up in tension between establishment Republicans and libertarian, Tea Party and religious conservative elements within the party. That fighting threatens to hurt the GOP as it tries to win an open Senate seat and begins to prepare for the 2016 presidential caucuses.