Monday’s ouster of Corey Lewandowski as Donald Trump’s campaign manager suggests the presumptive GOP nominee is at last shifting to a real general-election campaign.

Lewandowski helped Trump get farther than anyone expected a year ago — but apparently wasn’t the right guy to help him go the rest of the way. Lots of campaigns take longer to admit such unpleasant truths.

We doubt this means a huge shift in Trump’s strategy: He’s not going to bloat up his shop with hundreds of overpaid consultants. But he plainly needs to hire a few more quality people to help him focus his message.

Since locking up the nomination, Trump’s been hacking away at the golf ball — and too often slicing it into the rough. With the right coach, he should be able to slow down his swing and keep it in the green.

The No. 1 issue is still jobs and the economy. Trump needs to hit it, every day and in every way — and with an operation behind him helping get the message out.

He’s already outlined ideas on taxes and energy that can get America’s job-creation engine roaring. Hillary Clinton’s only answer is doubling down on Obamanomics — more taxes, more giveaways, more corrupt crony capitalism.

Democrats are adopting platform planks calling for a ban on fracking — the No. 1 source of US economic strength in recent years — and a “carbon tax” to kill even more manufacturing and mining jobs.

It’s lunacy on stilts — and the GOP nominee ought to be calling it out now, not getting distracted by the nattering of the #NeverTrump nabobs.

Election Day’s still over four months off, with a quarter of the voters still undecided. A bad week or two in June doesn’t mean much.

If Trump can hire as well as he always has, he’ll soon be back on his game, the polls will turn back around — and no one will be listening to his critics.