Trump third party
The Fox News Channel opposes this and made it the first issue of the 2016 presidential debate. But in 1980, it was a third-party candidacy by fellow Republican John Anderson which helped elect the conservative Ronald Reagan. Also, the third-party candidacies of Ralph Nader and Pat Buchanan helped elect George W. Bush in 2000, and the third-party candidacy of George Wallace in 1968 helped elect Richard Nixon. Indeed, the last 60 years suggest that is more likely for a non-incumbent Republican to win the presidency when there is a third-party candidacy, than when there is not.
The example often cited by Republicans for a third-party candidate "spoiling" the chances of a Republican to win the presidency was Ross Perot's candidacy in 1992. But an analysis of the polling data and Republican George H.W. Bush's approval rating (an unelectable 33%) demonstrates that the Ross Perot candidacy did not spoil Bush's chances of winning, and actually helped narrow the gap between him and Clinton. More people who had voted for Ross Perot in 1992 drifted to Clinton in 1996, rather than to the Republican Bob Dole, which reinforces the view that Ross Perot pulled at least as many voters away from Clinton in 1992 as from George H.W. Bush.
In 1996, Clinton won a slim majority of the overall votes, which tends to disprove the notion that Ross Perot was a spoiler in that race. The Republican nominee, Bob Dole, was a weak candidate from the moderate side of the party who had no chance of winning. Clinton's approval rating was well above 50%, which virtually guarantees an incumbent reelection.
Effect on the Media
In 2008 and 2012, in the absence of third-party candidacies, the liberal media were able to tee off against the Republican Party candidate in an unrelenting style. But when there is a significant third-party candidacy, as in 1968, 1980, and 2000, the media have a more difficult time being influential with its liberal bias.
Effect on Debates
The moderators and format for presidential debates tend to favor the Dems. As a result, Republicans tend to lose the presidential debates, with a few exceptions, dating back to 1960. In 1968 and 1972, Richard Nixon wisely refused to participate in the debates.
Effect on Swing States
Historically, the swing states have been Florida, Ohio, Nevada, North Carolina, and Virginia.
Trump quotes about 3rd Party candidacy
- Pressed on whether he would run as a third-party candidate if he fails to clinch the GOP nomination, Trump said that “so many people want me to, if I don’t win.” “I’ll have to see how I’m being treated by the Republicans,” Trump said. “Absolutely, if they’re [Republican National Committee] not fair , that would be a factor.” 
- "If they don't treat me well, Sean, why should I make that pledge?" Trump asked. "At this moment, it's great leverage, and I might as well use it." "I just want to be treated well and treated with respect." 
- "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." 
- Trump has also blamed Perot's candidacy for Clinton's 1992 win, "I think every single vote that went to Ross Perot came from 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." 
- "...I want to run as a Republican, not a third-party independent. I want to run as a Republican. As long as I’m treated fairly that is going to be a case. And fairly is an instinct. It’s an instinct. I know what fair is, you know what fair is. I know what it is, yeah, and I think that is happening. And by the way, win, lose or draw, I’m not just saying I have to win. Now I guarantee you this if I win the Republican nomination, I guarantee you all sitting there, I will not run the third party candidate, do you agree?” 
- Exclusive: Trump threatens third-party run, TheHill, July 23, 2015
- Trump on Possible Third-Party Run: 'Great Leverage, Might as Well Use It', FoxNews, August 7,2015
- Trump: I'm not thinking third party -- for now, WashingtonExaminer, July 7, 2015
- Donald Trump threatens to make Republicans' worst nightmare come true, BusinessInsider, July 23, 2015
- TRUMP: ‘I WAS THE ESTABLISHMENT’ TWO MONTHS AGO, August 11, 2015