Even with his antipathy toward stating policy positions, Trump has dropped enough hints here and there to provide an idea of what he thinks about issues central to the party platform.
Let's compare the party's words to those of the man who is currently best-positioned to be its next nominee, shall we?
Where they differ
2012 Republican party platform:
The Patient Protection and Affordable Care Act — Obamacare — was never really about healthcare, though its impact upon the nation’s health is disastrous. From its start, it was about power, the expansion of government control over one sixth of our economy, and resulted in an attack on our Constitution, by requiring that U.S. citizens purchase health insurance.
During the first Republican debate, Trump defended his past support for single-payer health care — that is to say, health care managed entirely by the government. "As far as single-payer," he said, "it works in Canada. It works incredibly well in Scotland. It could have worked in a different age, which is the age you're talking about here."
That apparently means that he thinks single-payer's time in America has come and gone. He went on to say that he'd like to see a private system. But praise of single-payer in any form is not at all common among leading Republicans.
Taxes, by their very nature, reduce a citizen’s freedom. Their proper role in a free society should be to fund services that are essential and authorized by the Constitution, such as national security, and the care of those who cannot care for themselves. ... Our goal is a tax system that is simple, transparent, flatter, and fair.
Trump disagrees with the idea of a flatter tax system. On "Fox & Friends" this week, he said, "The one problem I have with a flat tax is that rich people are paying the same as people that are making very little money. I think there should be a graduation of some kind." Meaning that wealthier people — like him — pay a higher percentage.
He also called for changing tax rules for hedge funds, who he said are "getting away with murder." Protecting hedge-fund managers isn't explicit in the Republican platform, but increasing taxes in any way is generally understood to be anathema.
We'll interrupt here to note what's interesting about these ideas from Trump: They seem likely to be pretty popular among the party's base, though not necessarily in the establishment. Sort of like...
We will create humane procedures to encourage illegal aliens to return home voluntarily, while enforcing the law against those who overstay their visas.
The 2012 Republican platform is nebulous enough that it doesn't conflict much with Trump's aggressive position. That's not an accident; immigration has been a point of tension between the GOP brass and its base for a long time.
But Trump's position is not that the party should "encourage illegal aliens to return home voluntarily" — it is that criminal undocumented immigrants should be deported and that protections against deporting non-criminal immigrants should be lifted. This is not "self-deportation;" it is deportation.
We oppose using public revenues to promote or perform abortion or fund organizations which perform or advocate it and will not fund or subsidize health care which includes abortion coverage.
In an interview with Sean Hannity on Fox News, Trump said he didn't think funding for Planned Parenthood (a key target of the "fund organizations which perform or advocate it" line above) should necessarily be cut.
Where things are murky
We support the public display of the Ten Commandments as a reflection of our history and of our country’s Judeo-Christian heritage, and we affirm the right of students to engage in prayer at public school events in public schools and to have equal access to public schools and other public facilities to accommodate religious freedom in the public square.
Trump has never claimed to be a particularly religious man, especially by the expected standards of Republican standard-bearers. At a religious gathering in Iowa in July, he said he hadn't ever asked God for forgiveness, which raised some eyebrows. His church says he doesn't show up much. Trump also declined to identify his favorite passage in the Bible when asked, but he has repeatedly called it his favorite book.
Where they agree
The institution of marriage is the foundation of civil society. Its success as an institution will determine our success as a nation. It has been proven by both experience and endless social science studies that traditional marriage is best for children.
Trump has attended gay weddings but says he opposes the practice — to the extent that he would not support the same-sex marriage of a grandchild.
We uphold the right of individuals to keep and bear arms, a right which antedated the Constitution and was solemnly confirmed by the Second Amendment. We acknowledge, support, and defend the law-abiding citizen’s God-given right of self-defense.
Trump told Ammoland magazine that he is a "Life Member of the NRA and [is] proud of their service in protecting our right to keep and bear arms." Again: This is an area where a vocal part of the Republican base shares Trump's opinion.
By whatever legislative method is most feasible, Old Glory should be given legal protection against desecration. ... We condemn the actions of those who deny our children the means by which to show respect for our great country and the constitutional principles represented by our flag.
This snippet from CBS News sort of says it all.