Donald Trump will become the GOP nominee for president. The odds are in his favor that he will be elected president as well. The reasons why are below the orange thingamewhatsit.
1. Almost everyone who read those first two sentences immediately scoffed. Trump is too...Trump. So? That is why he is leading in the polls. That is why his supporters support him. Tens of millions of people scoffed at Ronald Reagan for being Ronald Reagan. Tens of millions of people scoffed at George W. Bush for being George W. Bush. Candidates resonate with voters when they come across as individuals with distinct personalities.
2. The GOP base has a very strong anti-politician, anti-Congress streak. Mike Huckabee won the Iowa caucuses as a preacher not as a politician. Barack Obama's success came because his experience was so limited, not in spite of it. Mitt Romney was chosen by the GOP in 2012 because he ignored his stint as governor of Massachusetts. The GOP pack of senators and governors are virtually indistinguishable. Of the other non-politicians, Ben Carson is picking off the support Trump hasn't and Carly Fiorina, well....
3. The GOP, the party of business and people who think they are going to to strike it rich someday (inshallah), prefers successful people. Dwight D. Eisenhower's military success is legendary, as was Herbert Hoover's commercial success (and courage in Beijing during the Boxer Rebellion). Even George H. W. Bush was a successful oil man before he entered politics and his son co-owned a major league baseball team. Failure for the party usually comes when the GOP candidate is "just" a political success. Speaking of failure, what compels a failed CEO and failed Senate candidate to think she has any chance.
4. The GOP establishment is freaking out about Trump. If they think he needs to be stopped, they have concluded he can realistically win the nomination. Just look what Hillary Clinton's campaign has been doing in the face of Bernie Sanders' surge and Joe Biden's Hamlet imitation.
5. Trump and Carson both have a non-stick surface reminiscent of the venerated Reagan. It does not matter to their supporters what they say or who they say it to. They have the ability to be confident without looking smug and to be ridiculous without looking crazy. The GOP base praises forthright, irrational statements, opinions based on the Bible, bigotry, and bitterness. Sarah Palin still gets air time and she does look smug and crazy.
6. Does anyone really think Trump's second favorite book is Holy Scripture? Yes. A lot of people will not question anyone's opinions if the person says he is guided by God's Word (cue footage from Rowan County). This sort of thing has greater impact when it is a revelation about the candidate rather than something expected.
7. Reagan was elected because of his personality, message, and outstanding oratorical skills, not because he was once governor of the largest state. He asserted that government and the Soviet Union are evil and set about destroying both. His opinions were disturbingly unsubstantiated, but he was too charming for people to critically analyze what he said. Now, those attitudes have hardened within the GOP and parts of the rest of the population, substituting China, Mexico, Russia, etc. for the Soviet Union. Trump has equally great speaking skills as Reagan. He is pompous personally, but not condescending to audiences (just everyone else). He even shares weird hair with Reagan.
8. Trump has spent his adult life building and selling the Trump brand. Despite some major bumps, he has been hugely successful at letting the world know what "Trump" means. That brand is not a facade; the real Trump is already standing and lots of people like it. The real Obama was not revealed until after he was elected. No one in the GOP field seems real like Trump except Marco Rubio, George Pataki, and Ben Carson. Rubio seems to be running just to see how it is done. Pataki is the unique centrist in the group and can't even get noticed for being so ideologically different. Carson is right behind Trump in the latest polls. As for the Democrats, the real Clinton is there, but way too many people don't believe it, both supporters and critics. Sanders is certainly not hiding any aspect of his personality and O'Malley, Chafee, and Webb just seem to be hiding.
9. Trump will do anything to win, including promise not to run a third-party campaign. However, he signed that pledge because he strongly believes he will win the GOP nomination. If the GOP establishment somehow pulls the rug on Trump, he will have ammunition to claim he was the victim of the same old political intrigues that need to be removed from Washington. He will whip his supporters into having him denounce the pledge. That will not be necessary because Trump will win the nomination. He has the skill to outmaneuver the GOP poohbahs.
10. At present, Biden is the only one beating Trump in head-to-head polls, but Biden won't run and the polls are too close to be too reliable. Trump would love to see Clinton nominated; she is the anti-Trump on every level. For Clinton to beat someone as genuine as Trump, she would have to do everything Richard Nixon would do in her place and probably a bit more. The problem is that is what people think Clinton will do regardless given her machinations in the DNC. O'Malley, Chafee, and Webb are all pleasant enough and, given their invisible campaigns, probably in the mix to be vice president or a cabinet member if Clinton does not implode. Sanders poses the only true threat to a Trump presidency and then only if Sanders' grass roots supporters are successful at explaining to voters why the senator's approach to the issues is necessary for the US to recover from its decades-long decline and offers a clear framework compared to Trump's "I will figure it out when I have to" philosophy of governing.