Ed FitzGerald did a great job as the Cuyahoga County, Ohio, executive, reshaping a government fresh from an FBI investigation that led to dozens of arrests. Then, this year, he ran one of the worst statewide races in the country, losing by a big margin to Gov. John Kasich.

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It happens all the time in politics. Those who are great at one job might crash and burn when they try for another. It’s like the old Peter Principle, which was a fashionable notion in business some years ago.

People who do a good job keep getting promoted, until they reach a level that they aren’t suited for. “Perfectly talented people who are good mayors or good governors try to take it to the next level and just hit their limits,” says political historian Lewis Gould. “It’s really analogous to good college quarterbacks who flop in the pros.”

Think of Wendy Davis, who became a national political celebrity as a state senator, but lost badly in the Texas governor’s race last month. Naturally, in every election, someone has to lose. And plenty of politicians are successful stepping onto the next rung of the ladder. But there are reasons why some politicians who look like the most promising candidates ultimately aren’t fit for higher office.

For one thing, successful politicians are inevitably surrounded by people who are constantly telling them how great they are. “In Connecticut, every speaker of the House thinks he’s going to be governor,” says Matthew Hennessy, a Democratic consultant in the state. “When they step out of the Capitol building, nobody has a blessed clue who they are.”

And those used to being treated as a big fish in their own smaller ponds aren’t always equipped for the increased scrutiny that comes with running for higher office, where every mistake gets magnified and big-stakes opponents search for any weakness. “Moving up to that higher level, the environment can be so different that all the traits and little strategies you’ve come up with don’t apply anymore,” says Denver-based pollster Floyd Ciruli.

All this explains why a successful track record can sometimes be a handicap. If a person has been terrific for 20 years as mayor or in the legislature, he’s sometimes offered a clear run, with no real vetting by his own party.

In FitzGerald’s case, even though he had only held county office for a couple of years, Ohio Democrats cleared the field for him to challenge Kasich. Then, questions no one ever bothered to ask about a local official -- such as whether he was driving with a valid driver’s license -- helped doom his candidacy.