1. Barack Obama
Trump said in 2009 that Obama was "a strong guy who knows what he wants," a person with "the mark of a strong leader," and "totally a champion." He even bestowed the greatest Trumpian honor upon Obama, saying, "I would hire him."
In 2011, while considering making a run for president, he placed himself at the vanguard of the "birther" movement, demanding that Obama show his birth certificate and fueling suspicions that the president was not born in the United States.
2. Hillary Clinton
3. The Republican Party
From his book:
The Republicans, especially those in Congress, are captives of their right wing. The Democrats are captives of their left wing. I don't hear anyone speaking for the working men and women in the center. There is very little contact between the concerns and interests of ordinary people and the agendas of politicians. It was my observation of this gap between Americans and their "leaders" that led me to leave the Republican Party and join the Reform Party. The Reform Party carries a lot less baggage than the major parties. It has the opportunity to truly overhaul our political system in service of the American Dream
4. The 2009 stimulus package
Trump said that the economic stimulus package passed in 2009 to boost the slumping economy, widely denounced by conservatives, was "what we need" as a country.
5. Obama's environmental policy
In December 2008, Trump proclaimed his support for the appointment of Lisa Jackson as head of the Environmental Protection Agency.
"I know Lisa Jackson very well because I do a lot of business in New Jersey," Trump said. "She's a brilliant person, a great environmental person. And that's going to be an amazing appointment. You watch."
He said in June that he was not a believer in "manmade" climate change and that Obama "saying that climate change is the number one problem, it is just madness."
6. Hillary Clinton negotiating an Iran deal
Trump said in 1999 that, though he hated "the concept of abortion," he was "strongly pro-choice." He reversed his stance in 2011.
"I'm pro-life," he said then.
Michael Cohen, who was the executive vice president of the Trump organization at the time, noted, "People change their positions all the time, the way they change their wives."
8. Health Care
In 1999, while considering a run for president as a member of the Reform Party, Trump said he believed in universal health care as an entitlement from birth.
"I believe in universal health care. I believe in whatever it takes to make people well and better," Trump said, before adding that "it's an entitlement to this country if we're going to have a great country."
He said that year that as president he would fund a "comprehensive health care program" with "an increase in corporate taxes."
Trump has not abandoned his support for universal health care, but has now said that he would achieve that goal by negotiating deals with hospitals.
"I'm very expert on that stuff," he said earlier in July.
9. Taxes on the rich
10. Jeb Bush
Trump has been attacking Bush this cycle for being open to immigration reform, a position to the left of Trump's, calling him "weak" on immigration. And in June, Trump unleashed an array of insults at his fellow Republican presidential candidate, saying it was "embarrassing" Bush was beating him in the polls in New Hampshire.
"He's not strong," Trump said. "He's not powerful and he will never be respected to the point that you have to be."
In 2000, Trump said Bush was "bright, tough, principled," and "a good man." He donated $500 to Bush's 2002 gubernatorial re-election campaign.
11. Having another Bush in the White House
2000 Trump: "I like the Bush family very much. I believe we could get another president from the Bushes."
2015 Trump: "The last thing we need is another Bush, believe me."
12. John Kerry
In 2004, Trump called Kerry, who was then the Democratic presidential nominee, a "great guy."
"I know him," the Donald said in a Playboy interview published that October. "He's a great guy. He's a very smart guy. I think he's highly underestimated, and I think he's going to run an amazingly successful campaign. Look at what he did in the primaries. It appeared as if he was off the radar, and all of a sudden he made this great comeback. I have a feeling he's going to do very well."
In 2015, Trump has said Kerry "has absolutely no concept of negotiation" and strongly condemned the Secretary of State's decision to involve himself "in a bicycle race."
13. The assault weapons ban
14. Anthony Weiner
Trump donated to the 1997 re-election campaign of Anthony Weiner, a New York City Councilman at the time.
Weiner has since been plagued by sexting scandals, precipitating his resignation from the US House in 2011 and his withdrawal from the New York City mayoral race in 2013. In response, Trump handed down a series of blunt condemnations.
15. George Pataki
Trump wrote in The America We Deserve that he "was glad when George Pataki came to the governorship of New York," because of Pataki's promise to restore the death penalty.
That was before July 1, 2015, when Trump took to Twitter to rip into Pataki (who says he is also running for president), after the former New York Gov. condemned his remarks about undocumented immigrants.
16. Charlie Rangel
Trump said in 1999 that Charlie Rangel, the Democratic Congressman from New York, would be his top choice to be Secretary of Housing and Urban Development if he was elected president.
"I think Charlie Rangel is a terrific guy," Trump said that November. "He's a congressman from New York. He has been a powerful guy. Now the Democrats are not in power, but I think he'd be terrific at HUD."
The relationship between the two men seems to have deteriorated since then. In 2011, Rangel called Trump's potential presidential candidacy "an embarrassment to the United States."
Trump spoke favorably of action against Iraq in his book, The America We Deserve, saying he had wished then-President George H.W. Bush had finished the job during the Gulf War.
"We can learn something here from George Bush and see how good a president he was," wrote Trump.
"He wasn't afraid to use American power when he figured out that Saddam Hussein posed a direct threat to American interests in the East. I only wish , however, that he had spent three more days and properly finished the job. It is this kind of will and determination to use our strength strategically that America needs again in dealing with the North Koreans."
Trump also wrote in his book that if we attack Iraq we should "carry the mission to its conclusion," and that "Iraq remains a threat."
Consider Iraq. After each pounding from U.S . warplanes, Iraq has dusted itself off and gone right back to work developing a nuclear arsenal. Six years of tough talk and U.S. fireworks in Baghdad have done little to slow Iraq's crash program to become a nuclear power. They've got missiles capable of flying nine hundred kilometers—more than enough to reach Tel Aviv. They've got enriched uranium. All they need is the material for nuclear fission to complete the job, and, according to the Rumsfeld report, we don't even know for sure if they've laid their hands on that yet. That's what our last aerial assault on Iraq in 1999 was about. Saddam Hussein wouldn't let UN weapons inspectors examine certain sites where that material might be stored. The result when our bombing was over? We still don't know what Iraq is up to or whether it has the material to build nuclear weapons. I'm no warmonger. But the fact is, if we decide a strike against Iraq is necessary, it is madness not to carry the mission to its conclusion. When we don't, we have the worst of all worlds: Iraq remains a threat, and now has more incentive than ever to attack us.
By 2004, Trump was saying Bush would lose re-election because of Iraq, saying it might have cost his father re-election by taking Iraq action in the first Gulf War.
"Well, I think so. I mean, the economy is doing OK, not great, but the -- certainly Iraq has been a huge negative, as it was for his father. I mean, to be honest with you, I think that Iraq really hurt his father and possibly lost him the election, and I think that the Iraq could conceivably cost two Bushes the election," Trump said in one interview,
"Iraq has been a total catastrophe, and in the eyes of many it`s not about terrorism. I think he could have fought a much better war on terrorism by doing it differently. So Iraq has been a huge negative, I think, for Bush, and we`ll see whether or not it`s going to be the Achilles heel. It`s going to be a very close election."
By 2008, Trump was calling for Bush to be impeached, saying if then-House Speaker Nancy Pelosi impeached Bush it "would have been a wonderful thing."
18. John McCain
In 2008, Trump endorsed McCain for president. "I've known him, I like him, I respect him," Trump said on CNN that year, adding "he's a smart guy and I think he's going to be a great president."
On Saturday, Trump declared McCain "not a war hero," and has subsequently turned to attacking McCain on veterans issues to justify his comments. Trump added he thought McCain is only considered a war hero by some because he was captured.
19. Ronald Reagan and some of his foreign policy:
20. Rick Perry
Trump 2015: He's not a fan.
Trump 2011: He's a fan.