If Trump wins Republican candidate....

Don't hold your breath. It takes money to run a presidential campaign in the United States, lots and lots of money--and nobody is going to give that kind of money to a lost cause.

Is there a deadline for filing to run as an independent in some states?

Likely, the only hope for Cruz or Kasich at this point is a contested convention. And as much as hate agreeing with Trump, if he is not chosen as the candidate, there will be riots.

All the current Republican candidates signed the party loyalty pledge including Trump. It states that they'll support whoever wins the nomination. That said, I'm not sure how enforceable the piece of paper is. A third party run is possible.

Heck, Trump could be contested at the convention and thrown out of the party. Even he could go against the loyalty oath to run as a third party candidate.

They still could be write-in candidates (though that's a super crazy longshot).

http://www.npr.org/2016/03/16/470715857/erick-erickson-urges-republicans-to-prepare-third-party-alternative

There seems to be this ridiculous plan on the part of some conservatives that they can create a third party and have that third party win enough states to force the President to be decided in the House.

They seem to be under the delusion that if you run 2 Republicans of course that will mean Hillary won't get any Democratic votes in the usual democratic leaning states. Perhaps they don't understand the idea of plurality in a winner take all system.

That's goofy thinking. Seems to work heavily in Clinton's advantage. I hope they definitely try that doomed strategy.

It's amazing how insulated people seem to be from differing political opinions. Somehow they seem to think they can find a conservative candidate that will draw more from Hillary than from Trump. I suppose they believe their own propaganda about Hillary. She's so unlikable that no one wants to vote for her.

As one person pointed out, even if they pull 10% of the overall vote from Hillary (20% of Democratic support) which would bring her down to 40%, if the other 2 candidates go 25% and 35%, Hillary wins. I have a feeling even with another conservative candidate in the race that Trump's support is going to be in the 20-25% range minimum. I can't see any blue states abandoning Clinton to the point that she gets only 35% of the vote.

who does he think is going to throw money at the conservative candidate?

the Koch brothers have said they're fine losing the party/election this year - they want time to rebuild the party in a way that suits them

Donald Trump is the only republican candidate that I believe might run as a third party if he doesn't win the republican nomination. I just don't believe that any of the other major republican candidates would even consider running as a third party.

Yes, a republican running as a third party would clearly pull some votes from the other republican which would pretty much guarantee the democrats winning the White House. Yes, I would love to see happen.