As Andrew Prokop notes, the Trump campaign will likely compete with the likes of Sen. Ted Cruz (R-TX) for the ultra-conservative Republican base; after all, Trump's most notable contribution to national politics to date was pushing birther conspiracy theories so persistently that President Obama was forced to release his long-form birth certificate just to shut him up.
But the first time Trump seriously flirted with a presidential run, he sang a markedly different tune. In 1999 and 2000, he considered a bid for the nomination of Ross Perot's Reform Party, which was at the height of its influence after Jesse Ventura won the Minnesota governorship in 1998 as a Reform candidate. Trump's big idea was a one-time wealth tax of 14.25 percent on all individuals and trusts with a net worth in excess of $10 million. The proceeds would be used to wipe out the national debt, with the savings in interest payments going to shore up Social Security and pay for middle-class tax cuts.
This is a totally insane idea for a whole variety of reasons, many of which Bruce Bartlett ran through in the Wall Street Journal at the time. The tax wouldn't raise nearly as much as Trump thought it would, it'd encourage massive evasion (millionaires would move money around until they were worth $9.99 million and ineligible for the tax), and it'd force huge sell-offs of stock and other assets, leading to, as Bartlett writes, the "liquidation of thousands of businesses." Also eliminating the national debt just isn't that important, especially when (as in 1999) the government is running surpluses.
Interestingly, the closest thing to this that I've seen anyone other than Trump propose comes from noted socialist economist Thomas Piketty, in his bestseller Capital in the 21st Century:
This isn't directly comparable, since Piketty is suggesting this as an option if you insist on wiping out the national debt. He wasn't proposing it outright like Trump did. But it's still a startling similarity.
Piketty's much more notable proposal in his book is an annual global wealth tax with progressive rates ranging from 0.1 percent to 2 percent. Similarly, Edward Wolff, an NYU economist and the most vocal champion of a wealth tax in the US, proposed a plan in 1996 involving rates ranging from 0.05 percent to 0.3 percent. To the best of my knowledge, the highest existing wealth tax rate is Spain's top rate of 2.5 percent.
And among actual American politicians, even Bernie Sanders hasn't proposed a wealth tax like this; he's endorsed a big increase in the estate tax, and billed it as a "wealth tax," but it wouldn't be levied on the net worth of the living, like Piketty, Wolff, or Trump's proposed taxes would be.
"We must have universal healthcare," wrote Trump. "I'm a conservative on most issues but a liberal on this one. We should not hear so many stories of families ruined by healthcare expenses."
The goal of health care reform, wrote Trump, should be a system that looks a lot like Canada. "Doctors might be paid less than they are now, as is the case in Canada, but they would be able to treat more patients because of the reduction in their paperwork," he writes.
As far as I can tell, Trump has not mentioned his wealth tax plan again in the intervening 15 years. (Indeed, as of 2011 he was a vocal fan of making George W. Bush's tax cuts permanent.) But you can expect to hear a lot from his Republican rivals about how he'd tax success even more than Bernie Sanders.