She came, she saw, she flopped.

Kamala Harris had one job Tuesday night — to separate herself from the last four years of a failed administration and make a persuasive case that the next four years under her leadership would be like night and day. 

Achieving both goals would pose a challenge to even the most gifted and sincere candidate. Because Harris is neither, her claim that she’s ready for a promotion fell flat. 

No thanks, no sale.

She certainly gave it her best shot. Although her speech was predictably heavy on the dangers Donald Trump supposedly represents, it was otherwise good enough to serve as a closing argument, and her delivery was nearly flawless.

She sounded strong and looked almost as confident as when she delivered her acceptance speech at the party convention in ­Chi­cago.

Shadows looming

But a lot has changed since then and Tuesday offered no escape from the two shadows looming over her. One is Joe Biden, arguably the worst president in modern times and among the most unpopular.

To this day, Harris cannot say what she would do differently from Biden, which simultaneously makes her a blank slate and a full partner in a disastrous term. 

Even the setting of her speech — the Washington Ellipse, with the White House in the background — was a reminder of that baggage. 

It was an odd choice, with Biden just hundreds of yards away, perhaps watching her on television try to run away from him and their administration. 

She can’t get away with it because she often concedes she was the last person in the room with him for such terrible decisions as the deadly bug-out from Afghanistan.

Worse, she won’t admit a single mistake they made, which is an affront to the many millions of voters unhappy with the administration’s tenure, especially the Gold Star families and those who lost loved ones to illegal-migrant killers.

The other shadow looming over her, of course, is Trump, whose presidency was a roaring success compared to the last four years.

He has compounded her problems with a withering onslaught of criticism and by laying out specific and credible plans on the top issues — the economy, inflation, the border and America’s place in the world.

Nearly every poll shows that a majority of voters trust him more on those issues and believe they were better off with him in the Oval Office.

That Harris couldn’t escape the shadow of either Biden or Trump tells me she has run out of fresh arguments for her election. With early voting in full swing and Election Day next Tuesday, this was her last best chance to redefine herself, and she didn’t do it. 

Count it as one of many missed opportunities. Having wasted precious weeks hiding from the media and refusing to lay out specific policies she would pursue, she believed all she had to do was go scorched earth on Trump. 

Her assumption seems to have been that the legacy media would amplify her message and that by now she would be cruising toward victory. The media did their part, but, thankfully, they no longer have enough public power to pick presidents. 

Given her hatred for Trump, and the party’s dog whistles for violence, it’s also not unreasonable to believe Harris might actually have thought an assassin would solve her problems.

Although she finally dispensed Tuesday with the most odious references to Hitler and Nazis, she didn’t go cold turkey. Like a junkie, she needs her fix of calling Trump a “petty tyrant,” a “wannabe dictator,” and accused him of being “unstable” and “obsessed with revenge.” 

All quite remarkable when you remember that her White House broke 200 years of precedent by prosecuting Trump, trying to lock him up and keep him off the ballot.

Calling him a threat to democracy is the biggest lie in politics since Hillary Clinton called him a Russian agent. We know how that worked out for her. 

Another scurrilous effort by Dems is the naked appeal to race. Both of the Obamas created a new bottom by scolding black men who do not support her. 

Harris certainly played along, adopting various versions of southern accents when she spoke to predominantly black audiences. 

Stripped of all niceties, it’s an appeal that says all black Americans must vote for all black candidates. No wonder race relations are going backward at a rapid clip.

The flip side is one of the best parts of the campaign — Trump is picking up significant numbers of black and Latino voters. Our democracy works best when both parties have to scramble for every vote instead of taking them for granted based on race, gender or ethnicity.

Then again, it was probably inevitable that the Dems would finish the campaign in the gutter. Their decision — again, the Obamas were key players — to push Biden aside after his disastrous June debate performance set in motion a thoroughly undemocratic process. 

We still don’t know the full reason why the president agreed, but it almost certainly included a promise that he would be able to finish his term without threat of removal under the 25th Amendment. 

That means the cabal found him sufficiently cogent to be the commander in chief in a war-torn world but not cogent enough to be the candidate.

That sounds more like a love of power than a love of country.

But the party was able to pull it off because the media was as desperate to defeat Trump as the most rabid Dem. Notice that there have been few retrospective pieces on who knew what about Biden’s cognitive decline, and Harris gets away with insisting he was as sharp as a tack.

We are simply told it was time for him to step aside and pass the baton to her.

The immediate impact was euphoria, as the mountain of delegates that voted for Biden to be the nominee switched to Harris in a matter of hours. The party was jubilant not to have to lug his political corpse around any longer and the relief rally was soon dubbed the days of joy. 

But as summer turned to fall, and Harris revealed herself as not up to the job, the polls slipped and joy turned to panic.

That birthed the Nazi, Nazi, Nazi charges, which were outrageously offensive and may cost the Dems many Jewish votes. Internal polls must show as much, so there was Harris Tuesday night, attacking Trump as divisive while promising to be a uniter. 

She managed to keep a straight face while insisting, “We have to stop pointing fingers,” and declared that “I promise to seek common ground.” 

That sounds familiar because it echoes Biden’s inaugural address. As I wrote then, he used variations on the words “unity” and “together” more than a dozen times, as when he declared: ­“Today, on this January day, my whole soul is in this: Bringing America together. Uniting our people. And uniting our nation.”

He never tried, of course, and the divisions in America today are at least as great and definitely more heated than when Biden said those words. 

So now we are to believe his vice president, who can think of nothing she would have done differently over the last four years, when she makes the same promise. 

Fool me once . . .