Living in Missouri and editing a regional online publication, the SentinelKSMO.org, I got to watch the rise and fall of Missouri Gov. Eric Greitens up close.

Although I supported Greitens’ opponent in the primary, I voted for the little-known Greitens in the 2016 general election and was pleased to see him win.

And yet I could not forget the adage attributed to Winston Churchill, “If you’re not a liberal when you’re 25, you have no heart. If you’re not a conservative by the time you’re 35, you have no brain.”

Greitens decided he was a conservative Republican at 41. For Greitens, the journey took too long. He either had not enough brains or too much ambition or, as history proved, both.

Greitens declared himself a Republican in July 2015, just in time to run for governor of Missouri. The former Navy SEAL had an extraordinary resume.

Missourians gave him the benefit of the doubt on his party switch. Republican history, after all, is rich with compelling conversion stories.

Some of America’s most eloquent conservatives – like, say, Whittaker Chambers or David Horowitz – climbed out of the deepest Marxist swamps.

Others like Ronald Reagan moved gradually right as the Democratic Party moved left underneath them. Adults don’t move in the opposite direction. There was reason to welcome a warrior like Greitens and not to distrust his shift.

That said, many Missouri Republicans were skeptical of Greitens as a gubernatorial candidate. It was too much, too soon, too convenient.

His motive for switching rang false to those who had read Chambers’ “Witness” or Horowitz’s “Radical Son.”

Said the future governor in the way of explanation, “I became a conservative because I believe that caring for people means more than just spending taxpayer money; it means delivering results. It means respecting and challenging our citizens, telling them what they need to hear, not simply what they want to hear.”

For many, the explanation seemed too convenient, too shallow. As it turns out, the skeptics have had their skepticism rewarded.

Greitens, like Roseanne Barr, did not know Republican history well enough to know that conservatives are held to a different set of standards than are liberals – by the media, of course, but also by their fellow conservatives.

Greitens began the affair that would undo him while he was planning to launch his gubernatorial campaign. This was something a John Edwards would do, but Republicans know better. For a Republican, every media outlet might as well be a National Enquirer.

A stunningly inept St. Louis prosecutor almost rescued Greitens. In April State Rep. Paul Curtman filed a complaint with the Office of Chief Disciplinary Counsel against St. Louis Circuit Attorney Kim Gardner, the prosecutor in question.

Curtman cited any number of irregularities on Gardner’s part. These include her use of unlicensed private investigators, the enlistment of an out-of-state private prosecutor, the preparation of an indictment before an investigation, the absence of a written investigative report, inappropriate discussions with police officers and the failure to use the police appropriately.

Likely fearing that she would end up in more legal jeopardy than the accused, Gardner dropped the invasion-of-privacy charge against Greitens two weeks ago.

The judge in the case had granted a request by Greitens’ attorneys to call Gardner as a witness. She had every reason to fear the witness stand. Defense attorneys had accused her private investigator of perjury and accused Gardner of suborning it.

Relieved at the case being dropped, the Greitens camp started running TV and radio ads outlining, correctly, the politically motivated nature of Gardner’s prosecution.

Then, unexpectedly, Greitens resigned. The best explanation as to why comes from a former prosecutor named Bill Tackett.

According to Tackett, once a local Missouri judge ruled that a nonprofit called “A New Missouri” had to hand over documents possibly exposing the names of Greitens’ donors, the game was over.

“That was a giant can of worms that got opened up by that ruling,” said Tackett. “Instantly, that changed the playing field because that’s dark money, that’s something [donors] don’t want to get into.”

Tackett tied the governor’s improper use of campaign finances “to a lack of political experience.”

That inexperience betrayed Greitens in one crucial way: He failed to understand Republicans have to play by a much tougher set of rules than Democrats.

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