Republican presidential nominee Donald Trump told the congregation at Great Faith International Ministries in Detroit, Mich., that he attended service “to learn" and help remedy "injustice in any form." Trump's visit to the black church on Sept. 3 is seen as an appeal to African American voters. (The Washington Post)

AS THE presidential campaign enters its final stretch, this seems like a good time to ask: Will American voters allow themselves to be insulted, taken for granted and made fools of?

Donald Trump seems to be betting that the answer is yes. How else to judge his assumption that he can be elected without sharing basic information? He has released no meaningful health records. He has put forward virtually no serious policy proposals. Unlike every other major-party nominee of the modern era, he refuses to release his tax forms.

All of these would be essential reading material from any candidate, but the need for disclosure is especially urgent from Mr. Trump. He would be the oldest president ever elected, so his medical history is relevant. Unlike Hillary Clinton and, again, every other modern major-party candidate, he has no record of service in politics or public office by which he can be judged, so his policy intentions take on added significance. He has been on so many sides of so many issues that even serious position papers at this point would have limited credibility. But they would be better than nothing.

Because his claim to the presidency is founded on his claimed success as a businessman, his tax and financial records are particularly salient. Has he really made as much money as he boasts? Has he paid taxes? Has he sheltered money in the Cayman Islands, done deals with Russian oligarchs? Who knows? Not the voters — and, as far as Mr. Trump is concerned, there is no need for us to bother our little heads with such matters. As his son Eric said, “You would have a bunch of people who know nothing about taxes” — he means us dumb voters, in case you miss the reference — “trying to look through and trying to come up with assumptions they know nothing about.”

Ms. Clinton is not always a paragon of candor. But she has released far more information about her health; far, far more information on her policy goals; and decades of tax returns.

And here’s one more reason those tax returns matter so much: A taxpayer must attest to the truthfulness of his or her returns, whereas we know that Mr. Trump in many other arenas tells falsehoods. In a book, he boasts of his habit of “truthful hyperbole.” On the campaign trail, he repeatedly lies — Muslims celebrated in New Jersey after 9/11, Mr. Trump did not mock a reporter’s disability — and when confronted with contrary video or documentary evidence simply repeats his fiction. Post reporter David A. Fahrenthold has painstakingly exposed Mr. Trump’s falsehoods when it comes to charitable giving.

What else is he lying about? We don’t know, you don’t know, and Mr. Trump seems to believe we can all live with that. Can we? It’s a question Americans will have to answer on Election Day.