Jeff Flake, a Republican senator from Arizona, may stand up against the Republican president in 2020 — either as a Republican or an independent — if no one else does.

Flake's comments came on the eve of his first solo political appearance in New Hampshire, the state expected to host the nation's first presidential primary election in less than two years.

Flake is among a very small group of Republican elected officials speaking out against the Trump presidency with increasing alarm.

MANCHESTER, N.H. (AP) — Jeff Flake has a direct message for the Republicans of New Hampshire: Someone needs to stop Donald Trump. And Flake, a Republican senator from Arizona, may stand up against the Republican president in 2020 — either as a Republican or an independent — if no one else does.

"It's not in my plan to run for president, but I am not ruling it out. Somebody needs to stand up for traditional Republicanism," Flake told The Associated Press in an interview. "Somebody needs to raise that, for nothing else than to give people hope that that decent party will be back. We'll get through this."

Flake's comments came on the eve of his first solo political appearance in New Hampshire, the state expected to host the nation's first presidential primary election in less than two years. The 55-year-old Republican will deliver a speech Friday morning entitled "Country Over Party," as part of the esteemed "Politics and Eggs" speaker series at Saint Anselm College.

Flake is among a very small group of Republican elected officials speaking out against the Trump presidency with increasing alarm.

He has already written a book that slams Trump, condemned Trump on the Senate floor, and charged in a Thursday speech to the National Press Club that his party "might not deserve to lead" because of its blind loyalty to Trump. By visiting New Hampshire, Flake is now declaring the possibility of another tactic: a 2020 primary challenge.

On the ground in the Granite State, a full year before presidential candidates typically begin courting local voters, there is already an expectation among top Republicans that Trump will face a challenge from within his own party in the next presidential contest. Yet few think Trump could be defeated, even under the worst circumstances.

Steve Duprey, who represents New Hampshire at the Republican National Committee, said: "It's virtually impossible to beat an incumbent for the nomination. But that doesn't prevent people from trying with various degrees of seriousness."

"I think there will be some primary," he added. "Whether it's a serious contender or a protest candidate that the president's team would have to take seriously, it's too early to tell."

Despite Flake's fiery pronouncements, he would start out as an underwhelming presidential contender on paper.

He is not well-known, he has little money of his own and a disdain for fundraising, and because he is retiring from the Senate at year's end, he has no political organization to help fuel his ambitions.

Flake has powerful friends who could help, however, including the outspoken anti-Trump billionaire Mark Cuban.

"I'm a Jeff Flake fan," Cuban told The Associated Press.

The billionaire, who is considering a presidential bid of his own, acknowledged that he doesn't know much about Flake's political ambitions. "But as a citizen of this great country, the more candidates for the office of president the better," Cuban said.

Former New Hampshire GOP chair Jennifer Horn, a frequent Trump critic, said the GOP's struggles in recent special elections — in addition to Trump's near-daily struggles — make a primary challenge in 2020 more realistic than ever before.

"There is a path, there is a possibility, but it's such a narrow path that it's hard to see who the right person would be," she said, acknowledging she didn't know Flake very well yet.

In the interview, Flake acknowledged Trump was probably too popular among the Republican base to lose a Republican primary in the current political climate.

"Not today, but two years from now, possibly. Things can unravel pretty fast," Flake said, suggesting that a disastrous mid-term election season for the GOP could realign voter loyalty. "As soon as he's viewed as one who loses majorities in the House and the Senate, and there's no chance that someone in the 30s can win re-election, people might move on."

And if Trump's standing with the base doesn't fade, Flake would consider a presidential bid as an independent.

"I'm not ruling that out either," he said. "There are going to be a lot of other people in the party looking for something else."

He continued, "If you end up with Trump on one side, (Bernie) Sanders or (Elizabeth) Warren on the other, there's a huge swath of voters in the middle that make an independent run by somebody a lot more realistic."

Trump has a special relationship with New Hampshire.

The state gave him his first victory of the 2016 Republican primary season. He earned 35 percent of the vote compared with second-place finisher John Kasich, the Ohio governor who is also weighing a 2020 run.

And on Monday, just three days after Flake's visit, Trump is expected to make his first appearance in the state since winning the 2016 election.

Flake wants New Hampshire voters to know there's another option.

"This has been my party my entire life. I'm not willing to concede that this is permanent," he said.