SOUTHAMPTON, N.Y. — Phil Mickelson came here intent on breaking out the game to finally win the US Open.

Instead, the US Open finally broke him.

With one bizarre move and one ridiculous explanation, Mickelson turned a tournament referendum already focused on unfair conditions and unplayable holes into one on an unforgivable rule breach and an unimaginable mistake.

Yes that was Mickelson on Saturday afternoon, running down a hill on Shinnecock’s 13th green, catching up to his golf ball before it was done running past the hole, and then hitting it while it was still moving. Like a scene out of a family trip to the windmill-dotted mini golf course on the boardwalk, only this one was happening on the third day of a major championship, played out by one of the greatest golfers of all time, earning top billing precisely because this is the one major title said golfer just can’t seem to win on his desire for a career Grand Slam.

So, yes, Mickelson can be understood for losing his cool, for losing his composure, for losing his mind in that moment of frustration, scoring a 10 on No. 13. That’s what golf can do, especially on a course like Shinnecock Hills, particularly on a day when winds turned the greens into well-oiled bowling lanes.

That’s how anguish can come out, when the title you want so badly is slipping away, when the occasion of your 48th birthday is more than enough reminder that chances like these aren’t likely to come around much more.

But all Mickelson had to do was admit as much, to reaffirm his connection to the galleries as their everyman hero by echoing the mistakes of his US Open past with a simple, “I’m an idiot,’’ to beg their indulgence, if not forgiveness, for the momentary madness. Instead, Mickelson channeled that wide-eyed aw-shucks persona to its deepest degree, insisting this was a planned maneuver (despite witnesses attesting he had no idea of the ultimate consequence, which turned out to be a two-stroke penalty) to avoid further carnage.

“Look, I don’t mean disrespect by anybody. I know it’s a two-shot penalty,’’ said Mickelson, who shot 81. “At that time I just didn’t feel like going back and forth and hitting the same shot over. I took the two-shot penalty and moved on. It’s my understanding of the rules. I’ve had multiple times where I’ve wanted to do that, I just finally did it.’’

Except his words on the course said no such thing, not to the nearby rules official, who heard him admit he didn’t know what price he would pay, not to his playing partner Andrew “Beef’’ Johnson, who was gracious in calling it a “moment of madness’’ but who heard no explanation of understanding from the perpetrator.

“He just looked at me and just laughed. We just laughed at it. He had no words to say what he did,’’ Johnson said.

The word now is legacy, as in the threat the ever-popular Mickelson made to his own, not helped by ongoing defiance when he pulled the old “apology for how you feel rather than for what I did card,’’ with a terse, “If somebody’s offended by that, I apologize to them. But toughen up. This is not meant that way.’’

Only he doesn’t get to choose the response for this one, not on a day when he should have simply owned up to what he did.