But on Tuesday , the Arizona Republican said he would not seek a second term in the Senate. Both Republican and Democratic pollsters in Arizona said Flake’s approval rating has tanked in recent months, especially among Republican voters, as he clashed repeatedly with President Trump.

That Flake got crosswise with his home-state voters, who sided with their president over their senator, is a sign of an evolving party, one driven more by Trump’s words than Flake’s deeds.

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Flake came to Capitol Hill in 2001 as a reformer who wanted to end Congress’s big-spending ways. His arrival was one of the first signs that a new era of spendthrift conservatism was becoming fashionable.

“He was the Club for Growth’s first win. He was their poster child,” said Brett Mecum, an Arizona Republican strategist, referring to a major conservative interest group whose power has grown.

During six terms in the House, Flake acted as a thorn in the side of congressional leadership. He repeatedly forced votes to strip earmarks out of costly spending bills, embarrassing Republican colleagues who had to vote down his amendments to save their pork projects.

Every week for a decade, Flake’s office named an “egregious earmark of the week,” spotlighting government spending he thought was out of bounds in press releases often tinged with a humorous quip.

“Read my lips: no new earmarks,” Flake deadpanned in one release, highlighting $300,000 set aside for construction of the George and Barbara Bush Cultural Center at the University of New England.

Another winner: $150,000 for an actor’s theater in Kentucky. “It’d be nice if Congress starting acting more fiscally responsible,” Flake said at the time.

Flake may hold the distinction of being the only member of Congress to seek a seat on the powerful House Appropriations Committee with the explicit goal of ending or limiting earmarks.

Even as he needled his own leadership, Flake maintained a sunny disposition and good relations with the leaders he battled. Other Republicans who voted against leadership priorities lost their committee seats; Flake won the establishment’s support when he ran for an open Senate seat in 2012.

That year, Flake won what most Arizona Republicans expected to be the first of several terms.

But Flake watched his approval rating decline precipitously after taking issue with Trump, first as a candidate, then as a president. Some Republican insiders worried Flake was risking his career when he published an anti-Trump book earlier this year.

Flake acknowledged the changing face of the Republican Party as he announced his retirement Tuesday on the Senate floor.

Tuesday . “It’s also clear to me, in this moment, we have given up our core principles in favor of a more visceral anger and resentment [that] are not a governing philosophy.” “It is clear at this moment that a traditional conservative who believes in limited government and free markets … has a narrower and narrower path to nomination in the Republican Party,” Flake said . “It’s also clear to me, in this moment, we have given up our core principles in favor of a more visceral anger and resentment [that] are not a governing philosophy.”

Those fights have complicated and imperiled the Republican agenda, sewed bitter seeds between the two sides of Pennsylvania Avenue — and diminished Republican leaders in the eyes of their own voters.

As Flake was the harbinger of a new wave of fiscally stingy conservatives, so too has Trump foretold of a new generation of Republicans to come. This generation is unlikely to be as optimistic about their ability to change Washington as Flake was, even when he faced long odds.