How do you defend the indefensible? If you’re former state Senate Majority Leader Dean Skelos, you do the same as your Assembly counterpart, Sheldon Silver: You don’t.

Like Silver, Skelos opted not to testify on his own behalf — likely realizing the jury wouldn’t believe a word.

No, this was the gist of the closing argument from Skelos’ lawyer Wednesday: What the prosecution calls bribery, extortion and conspiracy was just business as usual — in a system everybody recognizes as corrupt.

It plainly is the way of Albany — but the public’s general awareness of corruption doesn’t make it legal.

Prosecutors nailed down example after example of Dean using his power to shake down companies to fill Adam’s pockets — $20,000 for a fake title-referral fee; $78,000 for a no-show job with Physicians Reciprocal Insurers, a $10K-a-month raise at another job with environmental company Abtech.

Abtech’s CEO cried he felt “held hostage” by the Skeloses.

Oh, the defense also played the Concerned Dad card — arguing, basically, that Dean steered work Adam’s way because that was the only way the no-account son could get by.

Probably true — but, as prosecutor Rahul Mukhi said, “You cannot commit a crime and then just say, ‘I’m not guilty because I did it to help my son.’ ”

Indeed, tons of New York corruption involves elected officials using their positions to enrich family and friends.

The particular scams in the Silver and Skelos cases may differ, but the payoffs-for-power pattern is plainly the Albany way.

If he keeps this up, US Attorney Preet Bharara can look at opening a probe of the whole Legislature under the racketeering laws.