PHOENIX — When news broke that Sen. Jeff Flake (R-Ariz.) would not run for re-election in 2018, many were at first surprised and then immediately wondered why.

Tuesday, a day after the announcement, Flake joined KTAR News 92.3 FM’s Arizona’s Morning News and explained that President Donald Trump and everything that he has brought in his first year of the presidency played a part.

“The Trump factor is a big one,” Flake said about his decision to not run. “I’m a traditional conservative that believes in limited government, economic freedom, free trade [and] immigration. The Trump factor is a lot different. [It is] very anti-immigration, very protectionist.

“But also it is the tone and tenor of politics, I just can’t abide the kind of vitriol and the kind of resentment that’s up front in terms of these politics.”

Earlier this year, and as recently as just a few weeks ago, Flake held fundraiser events that included former President George W. Bush and current senator from Florida, Marco Rubio.

Flake told Arizona’s Morning News his decision came in recent days.

“We didn’t make a decision fully until this weekend but this has been building,” Flake said. “I just knew that I couldn’t run a campaign that I had run in the past.

“It’s a very different party right now. It seems the No. 1 issue is ‘are you with the president.’ I just have a hard time understanding why a United States senator should need to be with the president on every issue. There are issues I agree with President Trump on and have worked with the administration on. But just like democratic presidents before and Republican presidents before, there are some things that I oppose. No senator should be a rubber stamp for the president.”

As for Flake’s future, that is a bit of an unknown but this is not part of a broader plan or higher aspirations.

“No, no,” Flake said. “If I had higher plans it would probably be better to stay in the Senate. No plans there.”

As for ever serving again, Flake did not rule that out.

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