Wisconsin Gov. Scott Walker eats a porkchop at the Iowa Pork Producers booth during the Iowa State Fair last month in Des Moines. (Daniel Acker/Bloomberg News)

The Post reports: “GOP presidential candidate Scott Walker — who has tumbled from top-tier status amid tepid debate performances and other missteps — will pull back from other early-voting states in favor of a heavy focus on Iowa, where he once led the field and has strong roots as a Midwesterner. The Wisconsin governor also faces growing pressure from some financial backers to make staffing changes in an attempt to turn around his campaign.”

Reporting on Walker’s self-inflicted wounds, we have observed that his backers and favorably inclined GOP veterans time and time again express amazement. How could a guy this disciplined be so gaffe-prone? How is it possible that the governor who stood up to the unions panicked when Donald Trump arrived? On one hand, this is the understandable reaction of sympathetic observers who underestimated Walker’s lack of presidential gravitas and policy deficits. It, however, is also indicative of the problems successful governors face when they go national.

An operative from a 2012 presidential campaign once remarked to me that governors see themselves as little emperors. They get the trappings of executive power. They ride in the big black cars with a security detail. They get to ride in a helicopter. They are often the best-known and best-liked pol in the state in which they have lived their entire lives. They are very big fish in a modest-size pond, which they easily mistake for a huge one.

With the benefit of experience governing and winning tough elections, they often look great on paper: balanced budgets, reformed state Medicare, increased test scores, etc. But with that comes the misconception that running for president is pretty much like running for governor. Hey, they’ve seen critical media before. No problem — they’ve had to prep for debates in the past. Alas, they have no idea that running for president is an entirely different ballgame. The vetting previously undergone at the state level means nothing. Old issues are raised and reexamined. Vetting will be repeated and amplified a thousand-fold. Their opponents will be far more skilled, and the media are more exacting. It’s not uncommon for a minor-league ace to get pounded when he faces big-league pitchers.

This syndrome is now familiar — Tim Pawlenty, Rick Perry in 2012 and Scott Walker. Early, unrealistic expectations and initial fund-raising success encourage such candidates to build a campaign team that is too large and expensive. If they falter in debates, the money dries up, the organization shrinks, panic sets in and they do poorly in Iowa and/or New Hampshire. It is over before it starts.

Seen in this light, the success of Bill Clinton and Ronald Reagan can be seen in perspective, as exceptions to the norm. These were once-in-a-generation political talents. In Clinton’s case, most top-flight Democratic contenders opted not to run that year as President George H.W. Bush’s popularity soared with victory in the 1991 Gulf War. In Reagan’s case, arguably his acting, public speaking, anti-Communist advocacy and even years as a Democrat were more instrumental in shaping a winning candidate than were his years as governor. He, too, was a larger-than-life character, one who just happened to be governor for a time. Frankly, a great TV personality is better equipped than a mild-mannered, excellent governor to run for president, as former Arkansas governor Mike Huckabee proves.

Looking at the 2016 field, it is easy to see that Walker was not prepared for the big stage, where one is bombarded with questions on new issues, where presidential stature is essential and where a significant state accomplishment (beating back the public employee unions) seems less impressive.

The one governor who, like Clinton and Reagan, might defy the odds is New Jersey Gov. Chris Christie. Just two years into office, party veterans in 2012 were begging him to run for president. Yes, his record was already strong, but it was his command of the stage, his ability to project confidence and his visceral connection with non-political and blue-collar voters (like Clinton and Reagan) that caught their eye. The plethora of candidates, Donald Trump mania and, of course, the faux bridge scandal have taken their toll on Christie, who appeared startled when another moderate governor, Jeb Bush, entered the race and started locking down donors. He still, however, retains formidable political skills. It is fair to say at this stage his chances of winning are much higher than Walker’s. His debate performances unquestionably have been better.

Walker is still in the race, and he and his campaign are putting on a good face. That said, he faces a very steep climb to attain his must-win victory in Iowa. He will need to contemplate whether it is better for him personally and career-wise to suffer an embarrassing loss in Iowa or to bow out earlier, as Pawlenty did.

Walker’s difficulty, if not predictable, was hardly surprising. The good news is that with no single, horrible “oops” moment, he might learn from the race, study intensely in the interim and come back for another presidential run. He’s a young guy and has 20 years or so to run for president. He just wasn’t ready yet.