President Trump should not be blamed for what the Republican Party has become, said Republican Sen. Jeff Flake, who believes the party's problems began during the Bush administration.

"I'm not blaming this lack of principle, or where we are, solely on the president. He's more the culmination of it," Flake told NPR in an interview.

The issue began around the time President George W. Bush was in office, the Arizona senator said. "This is a long time in coming. I got here in Washington in 2001. ... And we got [Bush's education overhaul law] No Child Left Behind, which was, I thought, big federal overreach into local education policy. And then we got the prescription drug benefit, which added about $7 trillion in unfunded liabilities. I didn't think that was a very conservative thing to do.

"When we couldn't argue that we were the party of limited government anymore, then that forced us into … things that we wouldn't have done otherwise if we would have been arguing about true principles of limited government or spending."

But now, Flake says he's "very troubled" about where the GOP is. "It seems that we've been compromised, but this time by different forces — those of populism and protectionism, isolationism, xenophobia and I'm concerned about how we remain a governing party with those principles."

Flake, who didn't endorse Trump during the presidential campaign, said the issues within the party have "made the ground fertile" for Trump. He recognizes the frustrations people have regarding jobs, their family's future, and economic future, adding that "Trump kind of spoke to that."

"I think as conservatives, our first obligation is to be honest with people and telling factory workers for example — it's always easier for a politician to point to a shuttered factory and say, ‘That's because of free trade. That's because Mexico took those jobs, or China did,' " he said. "But what is not recognized is that it's largely been productivity gains and automation."

On Sunday, Flake said Republicans need to work with Democrats to accomplish their agenda, as "there are big issues that we've got to solve." The failure of the "skinny repeal" healthcare bill and the upcoming tax reform legislation shows that "these are things that can't be done by one party. We've just seen the limits of what one party can do."