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WASHINGTON (CNN) — Scott Walker is dropping out of the Republican presidential race, according to a GOP strategist close to the campaign and a senior GOP adviser with knowledge of his plans.

The governor of Wisconsin entered the primary in July as a front-runner — a darling of both the conservative base and powerful donors after winning his battles against public unions in his left-leaning home state.

Walker has called a 6 p.m. ET news conference in Madison, Wisconsin, where he is expected to announce his decision to withdraw from the race.

The New York Times first reported Walker’s plans to drop out.

He rocketed to the front of the GOP pack in Iowa after a rousing speech at the Iowa Freedom Summit in January — and subsequently, his campaign pinned its hopes on the first state to vote in the presidential nominating process.

But Walker was hurt by lackluster performances in the first two Republican debates. And his poll numbers suffered: In a CNN/ORC poll released Sunday, Walker failed to garner even one-half of 1% nationally among likely GOP primary voters.

He was also hurt by reversals on a host of controversial issues — including birthright citizenship, on which he gave three different answers in the span of seven days. Those reversals were particularly damaging to his outsider image as non-politicians like Donald Trump, Ben Carson and Carly Fiorina climbed the polls.