Donald Trump's ongoing evisceration of the Republican Party establishment has earned him a reputation in some circles as a Teflon-coated magician, a politician whose mind meld with the American people is so strong it makes him immune to attack.

He's not.

Of course, liberals should not be complacent about Trump's ability to win a general election. Winning a primary is harder than winning a general, and anyone who's secured either major party's nomination is just a bit of good luck away from taking the White House. But the antidote to complacency is not panic.

The fact is that Trump has triumphed in Republican Party primaries because the Republican Party is incapable of mounting effective resistance to him, not because effective resistance is impossible. Their strategies have failed because highlighting his real weaknesses cuts against too much of what the GOP base believes.

The plain, obvious truth is that Trump is running a racist campaign based on an unimpressive record in business and bad public policy ideas. The Republican Party can't mount this argument in an effective way because to do so involves stepping over too many GOP taboos.

That's why to stop Trump, his opponent is going to have to be a Democrat — realistically, Hillary Clinton though in principle Bernie Sanders or someone else would work. A Democrat will happily hammer Trump over his weaknesses and bury a candidate who's already held in very low regard by the mass public.

Trump is a badly flawed candidate

There are three main problems with Donald Trump as a candidate for national office, none of which can be effectively exploited by the Republican Party but all of which can be exploited by Democrats. The problems are:

Trump is a racist.

Trump's business record is unimpressive and ethically dodgy.

Trump's policy ideas are terrible.

There is simply no reason to believe that this is what the American people are looking for.

The problem Republicans have is that is that these flaws are not flaws a Republican Party politician can effectively articulate to an audience of Republican Party primary voters.

Republican Party primary voters think that white people being shamed for racism is a bigger problem than white people doing racist stuff.

Republican Party elites are ideologically committed to the defense of inherited wealth and opposed to the regulation of business in the public interest.

Republican Party elites essentially share Trump's least popular and most obviously ridiculous policy idea — an enormous tax cut for the rich — so they can't criticize it.

This has left them resorting to a smorgasbord of hypocritical arguments and opportunistic cheap shots that don't have a clear takeaway, occasionally punctuated with the observation that Trump does not rigidly adhere to the GOP donor class's policy preference.

To the extent that this strategy could possibly accomplish anything, it's actually worked quite well — the GOP donor class has not given Trump money, they have given a lot of money to Trump's rivals, and they've induced the lion's share of donor-dependent Republican politicians to endorse Marco Rubio. The problem is that this strategy can't accomplish the thing that would cause Trump to lose: convince voters not to vote for him.

Democrats will not be so constrained. They can, and presumably will, press all three lines of attack effectively.

Trump keeps saying and doing racist stuff

Trump's roughest moment during the primary came when he hesitated to disavow David Duke and the Ku Klux Klan. It showed, momentarily, that he'd misjudged where the line is between the kind of "I'm-not-a-racist-I'm-just-not-politically-correct" stuff that plays with the GOP base and "okay, yeah, that's racist" stuff that doesn't.

But from saying Mexico is sending rapists north of the border to his embrace of the birther movement, Trump has been mainstreaming bigotry throughout his rise.

Other Republicans haven't been able to criticize him effectively in the context of a Republican Party primary because most Republicans don't think white racism is a problem. In a general election, Trump's problem will be that most Americans do think white racism is a serious problem. The Public Religion Research Institute's American Values Survey probably illustrates this best.

This is why short of embracing the Klan, leading Republicans did not bother professing to be worried about Trump's racism. Back during the 2012 primary cycle, for example, Trump first injected himself into politics by loudly endorsing racist conspiracy theories about Barack Obama's birth certificate.

Mitt Romney responded to this by seeking, obtaining, and touting Trump's endorsement in order to secure advantage in Republican primaries. Romney knew, at the time, that in the eyes of Republicans being accused of racism is a feature rather than a bug, because it shows you are against "political correctness," which is the real enemy.

Video: The bigotry that connects Trump with his audience

Trump got rich because he was born rich

The notion that successful businesspeople would make for successful politicians strikes me as dubious, but it's something voters have embraced in a number of races for statewide office over the years, and it's not totally shocking to see someone make it work on the presidential level.

That's why it's striking to note that though Trump is very rich, he's not all that successful a businessman. He's a guy who inherited a lot of money and achieved approximately average returns with it.

To give credit where due, the evidence suggests that the typical person would have drastically underperformed an index fund, so Trump's ability to roughly match one is at least slightly impressive. And he's clearly adopted a much more fun strategy than a passive investment portfolio.

But Trump's rise to economic, then cultural, and now political dominance is much more a cautionary tale about unearned privilege than it is an inspiring story of business success.

These are points Democrats won't hesitate to raise but that the Republican Party is institutionally incapable of making. The GOP, after all, is ideologically committed to the notion that heirs to multimillion-dollar fortunes are a currently oppressed class in the United States who ought to be allowed to inherit their fortunes tax-free, and that the uberwealthy in general ought to pay lower tax rates on their investment income. From inside this ideological dead end, Trump's rich dad can be raised as an insubstantial jibe but can't be incorporated into a broader ideological critique of Trumpism.

By the same token, Marco Rubio tried to note that Trump University was a scam and Trump's mortgage company was a scam and Trump in general seems to have run a lot of scams, but he couldn't incorporate this information into a coherent campaign, because he is ideologically committed to opposing any kind of meaningful business regulation.

In the hands of the Democrats, however, this all becomes an indictment of a rigged system in which the haves accumulate more and more political and economic power in a terrifying cycle of doom.

Trump's policy ideas are bizarre and unpopular

People say this year's Republican primary isn't about policy, and that's true — but that's in part because Trump's Republican opponents have chosen not to challenge him on policy. That's for good reason in the mirror universe of a Republican Party primary, but in general elections candidates argue about tax policy.

Trump is running on a comically regressive $11 trillion tax cut that will cost more than Hillary Clinton's entire progressive agenda while overwhelmingly benefiting a handful of superrich people. People like Trump himself.

What voters want, by contrast, is to redistribute wealth through heavy taxation of the rich.

Even rank-and-file Republicans have decidedly mixed feelings about giant tax cuts for rich people, but obviously none of Trump's opponents in the primary are going to hit him for this because they are all running on giant tax cuts for rich people.

Hillary Clinton has no such problem — she is running on the popular cause of making the rich pay more, while Trump is promising an enormous unpopular tax cut for himself.

The other issue on which he has real policy proposals is immigration. Trump favors mass deportation, which is what most rank-and-file Republicans favor even as most of the general population agreed with Hillary Clinton that creating a path to citizenship would be better. Trump also wants to reduce legal immigration, a position held by only about a third of Americans that, again, is popular with Republican primary voters.

Democrats might lose, but Trump is very vulnerable

None of this is a guarantee that Trump will lose a general election. He's wily and media-savvy. Clinton has vulnerabilities of her own. And, to an extent, any election cycle is hostage to the whims of events.

But nobody should mistake Trump's success in winning Republican primaries for unprecedented political genius, or the failure of his GOP rivals' attacks for invulnerability.

Trump has massive, obvious weaknesses as a candidate. He is a mediocre businessman who's become rich largely thanks to having a rich father and in part thanks to ethically questionable business practices. He is a longtime peddler of racist rhetoric and political concepts. He favors an enormous, unpopular tax cut for himself and people like him, and he is closely identified with immigration policy ideas that most Americans reject. His Republican Party rivals have been unable to leverage these points against him either because ideological conservatives are incapable of criticizing them or because rank-and-file Republicans embrace ideas that the general public does not.

That's why Republicans haven't stopped Trump so far, and it's why they won't be able to stop him in the future. To beat him, Republicans either need to replace their voters or adjust GOP ideological orthodoxy. They can't do the former and won't do the latter, so they have lost.

Democrats are not constrained in these ways, so they can — and likely will — stop Trump and keep him out of the White House.