WASHINGTON -- The last few weeks have offered Americans a chilling glimpse of three faces of Donald Trump: the stonewaller, the shape-shifter and the liar.

Trump the stonewaller has been on display in his refusal to release his tax returns. "It's none of your business," Trump flatly told ABC's George Stephanopoulos when asked about his effective tax rate.

Stephanopoulos: "Yes or no, do you believe voters have a right to see your tax returns before they make a final decision?"

Trump: "I don't think they do. But I do say this, I will really gladly give them."

Sure, he'd be happy to -- except that he isn't. And it is our business. Voters are entitled to know this information about a candidate for president, a person who would help steer the nation's finances. For decades, presidential candidates have routinely made this material available.

It is astonishing that Trump believes he is exempt from this norm -- that a pending audit makes his returns less important to see, not more, or that he is not obliged to find some other way of providing the information, such as returns from earlier years or summary data for the years still under review.

Even more worrisome is what this high-handed approach augurs for a Trump presidency; to airily promise transparency while repeatedly failing to deliver. It is an iron law of politics that candidates do not become magically more forthcoming once in office. Their behavior on the campaign trail, when under pressure to satisfy voters, represents a better version of what they would do on the job.

Then there is Trump the shape-shifter, a man without fixed views, and whose policy proposals are mere opening gambits. What does he believe? What is a core principle, and what is up for negotiation?

"I'm allowed to change," Trump told Stephanopoulos on the minimum wage (he didn't want it raised, then he did, now maybe not). Certainly, flip-flopping is a chronic and common political condition; it can be evidence of open-mindedness, rather than craven politicking or ideological spinelessness.

Yet Trump's proclaimed "flexibility" is unsettling because it does not rest on an existing edifice of long-expressed conviction and recorded votes. When everything is a starting bid, how are voters supposed to judge -- or guess -- where Trump might end up?

Trump's campaign is a vast policy desert, so declaring that the sparse fronds of detail are eminently negotiable erases any confidence that voters know what they are getting. Voting for Trump is like nailing Jell-O to your ballot.

Finally, most appallingly, Trump the liar. That is a strong charge, but it appears warranted in the matter of Trump masquerading as his own spokesman (disturbing enough) and then outright denying it (way more disturbing).

"It was not me on the phone," Trump told NBC's Savannah Guthrie. "And it doesn't sound like me on the phone. I'll tell you that. And it was not me on the phone. And when was this, 25 years ago?"

Yes, and Trump could have said any number of things: This was a silly prank, long ago. Of course he shouldn't have done it.

Instead, Trump opted to lie. How do we know? Because in a quote back then to People magazine about supposed spokesman "John Miller," Trump described his posing as "a joke gone awry." Because numerous reporters have described having similar encounters with phony Trump spokesmen.

Because Trump himself admitted in court that "I believe on occasion I used that name" -- referring to a different alias, "John Barron." Because who are you going to believe: Trump or your lying ears?

This is a fib, you might argue, so trivial as to be meaningless. Yet a candidate willing to lie about something so small will be a president willing to lie about something big -- and this is hardly Trump's only lie (e.g., thousands of Muslims celebrating in New Jersey on 9/11).

The popular understanding may be that all politicians lie, but there is a difference between the ordinarily distasteful political diet of spin, fudge, evasion and hyperbole and the Trumpian habit of unvarnished, unembarrassed falsehood.

"Who cares?" Trump would breezily assure the horrified Mar-a-Lago house historian after regaling guests with the untrue tale of how Walt Disney himself created the nursery-themed tiles in his daughter's room.

Who cares, indeed -- an important question for voters. Americans have elected previous presidents who subsequently lied to them (and, yes, that includes the husband of a current candidate). Knowingly electing one who lies while trying out for the job would be a tragic mistake.

(c) 2016, Washington Post Writers Group