Another theory on the government shutdown, this one from Chris Matthews: Maybe the protagonists were just too young to make a deal.

The MSNBC host spent the past 18 months obsessing about political leadership while writing “Tip and the Gipper: When Politics Worked,” a study of the relationship between Ronald Reagan and House Speaker Tip O’Neill.

“The Irish thing helped, but I think the most important thing between these guys and the reason it worked is they were both in their 70s,” Matthews said at his book party Tuesday. “For them, it was the big act as well as the final act, and they knew they couldn’t put it off with speeches and talk and positioning and crap. They had to make it work.”

That’s a different mindset from the today’s young Turks (Ted Cruz, Paul Ryan, Rand Paul, Eric Cantor ) who have years and years to make their mark — and less reason to reach across the aisle.

Is there a luckier author in Washington? Matthew’s perfectly-timed seventh book came out on the first day of the government shutdown; the party at P.J. Clarke’s happened to be scheduled for the night Senate elders put the final touches on a compromise deal.

The idea for the book began six years ago, when Matthews — who worked as a top aide to O’Neill in the 1980’s— spoke at the Reagan Library. He drew from Reagan’s diaries, the Speaker’s press conferences, newspaper clips, and a personal journal he kept while working on the Hill.

Much has been written about Reagan and O’Neill’s after-hours friendship. Matthews focused more on their “cordial and fighting” relationship: Despite differences, the two men respected each other as worthy opponents; Matthews describes them as “two great sluggers going at it and both looking good after the fight.” The men also shared a WWII-era respect for authority: “Tip was always, ‘Mr. President’ and Reagan was incredibly respectful of congress — and always understood that it was a co-equal branch,” he said. “Much more than Obama.”

On hand for the party: Three of O’Neill’s children (Susan, Rosemary and Kip, plus granddaughters), newly engaged couple Alex Wagner and Sam Kass, Rep. Debbie Wasserman Schultz, Sen. Ed Markey, former RNC chair Michael Steele, and a large contingent of Matthew’s media colleagues.