You’ve no doubt heard the timeless metaphor of the frog that was slowly boiled alive.

Had he been plunged into a pot of scalding water, he would have leaped out instantly.

Instead he was placed in a pan of cold water, and as it slowly heated he did not perceive any danger, so he remained incrementally comfortable until passively succumbing.

Does that not sound like America today as we’re lulled into enduring never-­ending assaults on our heritage?

The adage tells us we should not grow weary in doing well, but after so many battles it’s hard not to feel beaten down.

Tell God to take a hike; no more public mention of Him. OK.

Don’t teach history to our kids; just make sure they know we were the bad guys in every war we fought. OK.

Patriotism? Wrong. It might offend those who just got off the boat. OK.

Columbus Day? Never again. It’s now Indigenous Peoples Day. OK.

American culture is under relentless attack from those who thumb their noses at things the rest of us hold dear.

For too long we’ve been like that late frog, languishing in the tepid waters of inertia, until Donald Trump came along.

Remember the legend of the stonecutter who tapped a rock 99 times with no apparent effect? But on the 100th blow the rock split open.

Was it that 100th blow that did it? No. It was the cumulative effect of the preceding 99.

The 100th blow was just the straw that broke the camel’s back.

It’s hard not to think of that imagery when you consider what’s happening on the political landscape today. In state after state, representing all regions of this nation, Republican voters, sensing someone finally understands them, made it clear Donald Trump is their choice to right the wrongs that have been piling up for too long.

Indeed, he may be the straw that breaks this camel’s back.

Remember Howard Beale, the longtime TV anchor played by Peter Finch in the film “Network,” who was so apoplectic over what he saw as declining standards that he implored his viewers, “wherever you are,” to “open your window, lean out and shout ‘I’m mad as hell and I’m not going to take this anymore!’ ”

Throughout the long, grueling primary season that’s exactly what Trump’s supporters figuratively did, declaring themselves mad as hell and not willing to take it anymore.

Though persona non grata to the establishment, his popularity with everyday Americans continues to grow, suggesting that, at long last, this frog is poised to leap.