An old story from Albany is unforgettable. Gov. Nelson Rockefeller was a skilled arm-twister, but one legislator, a fellow Republican, resisted demands to vote a certain way, even rejecting offers of pork-barrel spending in his district.

Feeling triumphant, the legislator looked at Rocky and declared, “There’s nothing you can give me I don’t have.”

“Yes there is,” the governor ­responded cooly. “A primary opponent.”

With that threat, so the story goes, Rocky got his man.

The anecdote has always been a favorite for what it says about power and how successful pols use it. Rockefeller, like Lyndon Johnson, believed every legislator had a price — he just had to find it.

Which brings us to President Trump, and his growing problems with congressional Republicans. Too many are bucking him, making it hard to get big things done.

Even before the collapse of ObamaCare repeal, the president felt abandoned by his party because few had risen to defend him from special counsel Robert Mueller. “It’s very sad that Republicans, even some that were carried over the line on my back, do very little to protect their President,” he tweeted, a theme one of his sons elaborated on Monday.

“I want somebody to start fighting for him,” Eric Trump told Sean Hannity on Fox News. “My father has the voice of this country. The people of this country love him. Why wouldn’t they [Republicans] get in line?”

He added, “It doesn’t make sense.”

Actually, it does make sense — political sense, which should never be confused with common sense or any other sense.

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