Donald Trump's 2016 presidential run seems custom-made for a third party. The billionaire developer has never held political office, never run as a Republican or Democrat. He doesn't need a party's money-raising apparatus. His anti-politician appeal — "Politicians are never going to bring us to the promised land" — cuts equally against Republicans and Democrats. And as far as Republicans are concerned, Trump appears to connect with GOP voters who are so disgusted with the party's current Washington leadership that they would be open to a third-party campaign.

But in an interview Tuesday, Trump said he has no interest in running as a third-party candidate, at least for the moment.

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"I've had many, many people ask me about running as an independent," Trump told me in a telephone conversation. "My sole focus is to run as a Republican. I'm a conservative Republican."

"My sole focus is to run as a Republican," Trump repeated, "because of the fact that I believe that is the best way we can defeat the Democrats."

When I asked Trump to elaborate on why he would stay in the GOP, Trump cited his rising position in the polls, the big crowds he attracts, and his profile in the race. "We've hit a nerve," he said.

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Still, Trump could hit a nerve as a self-funded independent. And as an independent, he would not be subject to the "three tickets out of Iowa"-style analysis that can put pressure on candidates who don't succeed early. So why tie himself to the GOP? "I believe I'm the only one who can beat Hillary Clinton," Trump explained. "Having a two-party race gives us a much better chance of beating Hillary and bringing our country back than having a third-party candidate."

At that point, I asked Trump about Ross Perot's third-party run in 1992, in which Perot won 19 percent of the popular vote. Did Trump believe Perot was a spoiler in that election?

"Totally," Trump said. "I think every single vote that went to Ross Perot came from [George H.W.] Bush…Virtually every one of his 19 percentage points came from the Republicans. If Ross Perot didn't run, you have never heard of Bill Clinton."

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In the course of a brief talk, Trump made a strong case for staying in the Republican party. But he left the door ever so slightly cracked at the end, when I asked if he would definitively rule out a third-party run. "It's something I'm not thinking about right now," Trump said, "because I'm doing well within the Republican ranks, and that gives us the best chance of defeating Hillary Clinton."