Few moments in Hillary Clinton’s long career have become her more than her speech of concession to Donald Trump. How much Mrs. Clinton wanted the presidency was evident — too much so, maybe, but it’s an understandable ambition — to all her countrymen. It took some bravery to acknowledge the pain of defeat so publicly and with such grace. She set an example for millions, none more important than the millions of girls who dream of scaling the height that Mrs. Clinton came so close to conquering.

Yet it is the part of honesty to acknowledge that Mrs. Clinton is the author of her own defeat. She had huge advantages in this race — much more money than her billionaire opponent, a resume that included not only First Lady but senator and state secretary, a political machine greater than anything the boys of Tammany dreamed of, and a national press corps almost uniformly in, if not her pocket, at least her corner. All that was squandered by blunders large and small.

The Clinton Foundation was a huge error, and not just because of the miasma of corruption, although that was evident to even some of her most ardent admirers. The error was even more inherent. The foundation’s work is spending — or giving away — other people’s money. Yet Americans are tired of the government spending or giving away their money. They have run out of money. The government she wanted to run is even worse than the foundation — the money it gives away, after all, it wrests from the taxpayers at the point of a gun.

Mrs. Clinton’s private e-mail server was another error, as was her support for the appeasement of Iran. Her attempt at a Russian reset was an error, as was her failure to stick with the struggle in Libya after she obtained the no-fly zone and toppled the Libyan dictator, Muammar Gadhafi (also an error was her laughing boast “We came, we saw, he died”). She erred in abandoning her support for the war in Iraq after voting to send our GIs into battle. She erred in positioning herself between Israel and her adversaries.

One could go on and on about these details. But Mrs. Clinton’s biggest, and least remarked-upon, error was abandoning her seat in the United States Senate to serve as state secretary to the man who defeated her first attempt on the presidency. What in the world was she thinking? It’s not just that one would have to go back to Martin Van Buren to discover a state secretary who made it to the White House. (The others were Thos. Jefferson, Jas. Madison, Jas. Monroe, John Quincy Adams, and Jas. Buchanan.) And it’s more substantive than that.

Had Mrs. Clinton foresworn ambition and lurked in the Senate, she could have become within the Democratic Party the leader of the loyal opposition to its left wing, led by, in Mr. Obama, the president she tried so hard to defeat in the primaries. She could have had any committee assignment she wanted, and, by dint of her enormous abilities, could have emerged as a titanic figure in the world’s greatest deliberative body. She could have led the effort against a retreat in Iraq, and against the reduction in our military outlays.

Had she stayed in the Senate, Mrs. Clinton could have served as a reasonable voice against the hard-left’s superstar, Senator Warren. She could have involved herself in the oversight of the Federal Reserve. She could have sought to lead the effort that Senator Schumer failed to lead against the appeasement of the Iranian ayatollahs. She could have fought day and night for the kind of approach to immigration she spoke up timidly for during her years at State and after.

Is all that day dreaming? The Washington Post’s greatest sage, J. Russell Wiggins (now, sadly, gone), rarely lost a chance to remind his friends that history does not disclose her alternatives. And we have often said that we’re not haters of the Clintons, neither Hillary nor her husband. All the more reason to reflect on this mother of all errors. Mrs. Clinton went to work for, in President Obama, a man with whom, she spent 2008 telling us, she doesn’t agree. Then she was bound in the shallows and now the miseries and her graceful l’envoi to what might have been.