Sen. Jeff Flake doesn't mince words when it comes to conservatives' hand in the rise of Donald Trump.

The Arizona Republican, in an excerpt of his new book, Conscience of a Conservative: A Rejection of Destructive Politics and a Return to Principle, says it plainly:

"It was we conservatives who rightly and robustly asserted our constitutional prerogatives as a co-equal branch of government when a Democrat was in the White House but who, despite solemn vows to do the same in the event of a Trump presidency, have maintained an unnerving silence as instability has ensued," the excerpt, published Monday in Politico, reads. "To carry on in the spring of 2017 as if what was happening was anything approaching normalcy required a determined suspension of critical faculties. And tremendous powers of denial."

The excerpt from the book, which goes on sale Tuesday and takes it name from one written by the late Barry Goldwater, tells of Flake's dissatisfaction with how the Republican party has responded to the president.

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"Too often, we observe the unfolding drama along with the rest of the country, passively, all but saying, 'Someone should do something!" without seeming to realize that someone is us," he writes. "And so, that unnerving silence in the face of an erratic executive branch is an abdication, and those in positions of leadership bear particular responsibility."

It's worth noting that Flake is up for a battle of a re-election in 2018 and has voted for policies favored by Trump, including last week's "skinny" Obamacare repeal.

He offers Republicans some ideas of what to do next:

"First, we shouldn't hesistate to speak out if the president 'plays to the base' in ways that damage the Republican Party's ability to grow and speak to a larger audience. Second, Republicans need to take the long view when it comes to issues like free trade: Populist and protectionist policies might play well in the short term, but they handicap the country in the long term. Third, Republicans need to stand up for institutions and prerogatives, like the Senate filibuster, that have served us well for more than two centuries."

Read the excerpt here.