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A prominent conservative activist and fundraiser is reportedly threatening to steer donors away from the Republican Party if GOP lawmakers agree to raise taxes.

Brent Bozell, founder and president of conservative watchdog group Media Research Center, sent a letter to Republican National Committee (RNC) Chairman Reince Priebus on Wednesday promising to advise conservative donors to shun the party if its leaders in Congress sign a deal to raise taxes, The Hill reports.

Bozell — who is also the chairman of ForAmerica Inc., a Virginia-based nonprofit — has been active in conservative political circles for three decades and estimated he has raised hundreds of millions of dollars for a litany conservative causes.

“Reince, it pains me to say this, but if the Republican Party breaks its word to the American people and goes along with President Obama with tax increases, it will have betrayed conservatives for the final time,” Bozell wrote. “I will make it my mission to ensure that every conservative donor to the Republican Party that I have worked with for the last three decades — and there are many and they have given tens of millions to Republican causes — gives not one penny more to the Republican Party or any member of Congress that votes for tax increases.”

A spokesman for the RNC did not respond to a request for comment, The Hill reports.

Separately, Bozell also sent letters to House Speaker John Boehner and Senate Republican Leader Mitch McConnell earlier in the week, pushing them to reject Obama’s call to raise taxes on the wealthy.

“With the so-called ‘fiscal cliff’ rapidly approaching, both sides are making opening gambits and the talk so far is alarming,” Bozell wrote in a letter dated Tuesday to Republican leaders.

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