Sen. Jeff Flake said Sunday that he had not considered leaving the Republican Party, despite his critique that conservatives are failing to assert independence from President Donald Trump.

In an interview on NBC’s "Meet the Press," the Arizona senator said he was "not at all" thinking about breaking from the party and that he was a "lifelong Republican." Flake is facing a potentially tough re-election campaign next year.

"Arizona tends to elect independent-minded people and people who stand on principles," he said. "So I’m doing what I think my voters expect of me."

Flake is promoting a new book, "Conscience of a Conservative." In an excerpt published by POLITICO, Flake wrote that Republicans shouldn’t hesitate to speak out against Trump if he takes actions that "damage the Republican Party’s ability to grow and speak to a larger audience."

In the interview Sunday, Flake was asked about his Senate voting record, which has been supportive of Trump’s policies, and whether there was a point where he would vote against his own ideological interests to send a message to Republican leaders.

Flake argued that the Senate has been focused on confirming Trump’s appointees, including Supreme Court Justice Neil Gorsuch. Flake added that Trump was on the right track with regulatory policy and had "good instincts" on tax reform.

"But on many things like trade, I expect to vote against the president," he said.