Liberals don't realize it yet, but they are poorly equipped to defeat Donald Trump in the general election. Their normal tool of attack - pointing out the moral/ideological flaws of their opponent and shaming him/her - won't work with The Donald because The Donald has no shame.
What's more, Trump's supporters and potential supporters simply don't care that he says racist and misogynist things. It's simply not important to them.

That doesn't mean Trump can't be beat by a liberal. It means that liberals must pay attention to what Trump and his supporters are saying if you want to beat him.

“When the going gets weird, the weird turn professional.”
- Hunter S. Thompson, Fear and Loathing on the Campaign Trail

Contrary to what the liberal echo chamber might believe, the defining characteristics of Trump isn't racism and sexism. The defining characteristics of Trump are narcissism and being a bully.

nar·cis·sism: Symptoms include an excessive need for admiration, disregard for others' feelings, an inability to handle any criticism, and a sense of entitlement.

Trump seems to have an almost complete lack of self-awareness. He may not even be aware of how he appears to others.
That is remarkable because he seems to be very perceptive of the weaknesses of others. Both features make him a very effective bully.

Trump has turned both of these personality traits into a sort of proto-fascism.
Which makes it so ironic that Trump recently tweeted a Mussolini quote.

The quote doesn't espouse racism or totalitarianism. I'm not even sure Trump holds any views at all -- at least not for much longer after words leave his mouth. He does, however, know what words will resonate with people who are angry and tired of losing.
Trump doesn't use language to communicate information. He uses it to elicit emotion. His utterances are weaponized sound, not speech. Information is complex, and knowledge is spotty on all sides. Emotion dressed up as information is simple and powerful. Fact-checking is simply extraneous to what's going on.

“The main problem in any democracy is that crowd-pleasers are generally brainless swine who can go out on a stage & whup their supporters into an orgiastic frenzy—then go back to the office & sell every one of the poor bastards down the tube for a nickel apiece.”
- Hunter S. Thompson, Fear and Loathing on the Campaign Trail

That's an important point that liberals have almost completely overlooked. Trump supporters have been losing for a long time and are angry. Liberals must address that fact and soon, because Trump didn't create this movement and it didn't fall from the sky. Therefore it will be back in four years if it is ignored.

So how does all this information help defeat Trump? It tells that reason and high-minded arguments aren't going to defeat him.
To beat him you are going to have to hit him at the gut level.
You are going to have to undermine the very foundation of his persona - that he is a winner.

Just listen to his speeches and debates.
His campaign rests entirely on the premise that he will beat up on weaker people for all of us, just like an eighth-grade bully who want to be your friend.
Trump will tell you how strong he is. What an Alpha Male he is.
Most of all, Trump will tell you how much he wins.

Trump's strength is also his biggest weakness. If people start to doubt Trump is a winner then he is finished.
Between his failed marriages, his tax records, and his bankruptcies, there is plenty of opportunity here, and John Oliver makes a good start.

There is also a flip side here - deflecting his attacks.
Unfortunately, the Democratic establishment has decided to run a status quo candidate this year.
That's going to make it harder.

But if you asked a computer to design a Democratic candidate who'd be the wrong standard-bearer against Trump, it could hardly improve on Hillary Clinton.
Trump, seemingly, is vulnerable on wild inconsistencies that will be easy marks for Democrats and the media. But for every Trump liability, Clinton has her own blemishes that Trump will wail on....The trouble is, at age 68 and with a long and well-documented record, Clinton is well past the age where she can re-invent herself with any credibility. It's hard to imagine what might rouse the enthusiasm of the Sanders base for a Clinton candidacy

The Democratic establishment was incredibly tone-deaf to the feel of the voting public this year. In a year in which the public is rebelling against institutionalized corruption you don't run a candidate that people don't trust, who is under an FBI investigation, and that promises more of the same in an economy in danger of falling into a recession.
That's not a good equation.

But you have to play with the cards that you are dealt.

You can already see where this is going. Trump hinted at it last August.

Without missing a beat, the real estate tycoon continued: “I was a businessman. I give to everybody. When they call, I give. And you know what? When I need something from them, two years later, three years later, I call them, and they are there for me.” He added, “And that’s a broken system.”
Repeatedly asked what he got in return for his donations, Trump said: “With Hillary Clinton, I said be at my wedding and she came to my wedding. You know why? She didn’t have a choice because I gave. I gave to a foundation that, frankly, that foundation is supposed to do good.”

All it takes is just a little exaggeration and this could be the moment in the general election debate that defines the election. Trump doesn't even have to lie, just message the truth a little.
Wave a few donation receipts at the camera and mention that if you want Hillary's opinion on the matter you can catch her outside of federal court, and voters will lap it up. If the Clinton campaign isn't ready for it this could throw the election.
I don't know what the response should be, but I do know there has to be one.

I would suggest Hillary gets out in front of this. Bring up the corruption in the system and explain what she is going to do about it.
Otherwise it'll be the elephant in the room just waiting for Trump to point it out.