For two decades he's been tracking presidents this closely. His records are so impeccable that colleagues routinely ask Knoller to clarify the minutest of presidential details. He has even corrected the White House's calculations. All of which makes him perfect to put criticism of Obama's frequent trips to the golf course in historical context.
Leading that drumbeat was Republican National Committee Chairman Michael Steele. "While it is fitting and appropriate to look at the yachting activities of the BP CEO with incredulity, it is equally incredible that President Obama finds himself on yet another golf course as oil continues to spew into the Gulf," reads a recent RNC statement.
Steele's assertion assumes that a president's tee time hinders taking care of business. Far from it. Time spent outside the Oval Office benefits the man - and the American people - the next time a crisis develops.
Consider a bit of information from Knoller's records. As of last week, Obama had played 39 rounds of golf and taken 33 vacation days during his 17 months in office.
By comparison, George W. Bush spent all or part of 490 days at his ranch in Crawford, Texas, over his eight years in office. Not to mention the 487 days he spent at Camp David, according to Knoller.
In fact, Bush 43 used to give Knoller a workout about his calculations. "If I arrive at the ranch late on a Friday, you count it as a whole day," he recalls the former president lamenting.
The Clintons - "the First Family that were really homeless," Knoller noted - didn't have a home outside the White House. According to news reports, Bill Clinton had spent all or part of 152 days on vacation by December 1999.
Among them were two summer trips to Jackson Hole, Wyo., recommended by political strategist Dick Morris, whose polling indicated that the American people liked their president vacationing near the mountains as opposed to Martha's Vineyard.
Over the course of his eight years in office, Ronald Reagan spent almost a year at Rancho del Cielo near Santa Barbara, Knoller told me.
Those trips were a top-down directive. In her book Reagan: An American Story, Adriana Bosch recounts a conversation between the Gipper and deputy chief of staff Michael Deaver early in their time at the White House. Deaver entered the Oval Office to find Reagan at his desk inspecting his schedule - which, the president lamented, didn't include "any ranch time." Deaver told him that was because the press had been critical of Reagan's spending so much time outside of Washington.
Reagan's answer: "You can tell me a lot of things to do, and I'll do them, but you're not going to tell me when to go to the ranch. I'm convinced that the more often I get out to the ranch, the longer I'm going to live, and I'm going to the ranch. So you might as well put it in right now."
Being "on vacation" doesn't mean the same thing to a president as it does to the rest of us. To have the job is to be always plugged in and ready to take a call or make a decision. The black briefcase containing the nuclear launch codes is never more than a few steps away, Knoller noted. "He may be taking a breather. He may be [in] a change of venue. But is a president really ever on vacation? I don't believe so," Knoller said.
There is another consideration. The White House is a 24/7 fishbowl. There are nonstop pressures, constant media attention and public curiosity, and the frenzied nature of life in Washington. Because it functions as both the president's workplace and the First Family's home, there's an enormous and chaotic staff presence there at all times. I don't blame the First Family for leaving 1600 Pennsylvania Avenue.
Which is why no one should begrudge a president a couple hours twice a month for golf. Or time to clear a bit of brush between briefings. Or a moment to enjoy a glass of wine at the Vineyard, or a horseback ride at his ranch.
The health of the country is largely a function of the physical and mental health of its commander in chief. If blowing off some steam with a couple of bogeys and a beer in the clubhouse keeps him sharper when the red phone rings, we're all better off for it.
Contact Michael Smerconish via www.smerconish.com.