Sen. Jeff Flake, R-Ariz., will not seek re-election next year, issuing a sharp rebuke to a Republican Party that he said has given into a "more viscerally satisfied anger and resentment" under President Donald Trump.

Flake, who drew Trump's ire when he published a book criticizing the GOP's current identity, considers himself a traditional fiscal conservative. He faced a brutal primary fight from the right from at least one candidate who alleged he did not do enough to support the president, while he had a general election challenge from the Democrats in a state that is far from a lock for Republicans.

His sudden decision, first reported by The Arizona Republic, generates uncertainty around both his Arizona seat and the GOP's 52-seat Senate majority.

In a stinging Senate floor speech announcing his decision, Flake eviscerated not only the "coarseness" of the national dialogue but also those in the Republican Party who insist on following Trump's lead. He contended that "reckless, outrageous and undignified behavior" coming from the executive branch has gotten "excused."

"And so, Mr. President, I will not be complicit or silent," Flake said. "I decided that I would be better able to represent the people of Arizona and to better serve my country and my conscience by freeing myself of the political consideration that consumed far too much bandwidth and would cause me to compromise far too many principles."

"To that end, I am announcing today my service in the Senate will conclude at the end of my term in early January 2019," Flake continued. "It is clear at this moment that a traditional conservative who believes in limited government and free markets, who is devoted to free trade, who is pro immigration, has a narrower and narrower path to nomination in the Republican party — the party that has so long defined itself by its belief in those things. It is also clear to me for the moment that we have given in or given up on the core principles in favor of a more viscerally satisfied anger and resentment."