Blame Wisconsin Gov. Scott Walker's vast financial edge or independent voters' uneasiness over using a recall election to oust an incumbent for policy differences. Political analysts have pointed to both these reasons for why Democrat Tom Barrett's lost in the June 5 gubernatorial recall. But they've also said Barrett was hampered by his current occupation: Mayor of Milwaukee.

Many of the ads supporting Walker spotlighted Barrett's two terms at the helm of the state's biggest city, blaming him for tax hikes, spending increases, high unemployment and crime. Walker and his allies were "really hammering Barrett about all the social ills in the city," said one Wisconsin political observer in the run-up to the recall. "On balance, I think being the mayor has hurt him a bit statewide."

Washington Post political blogger Chris Cillizza agreed. He wrote after the election that "Barrett's ties to Milwaukee … wound up hurting him far worse than many Democrats expected at the start of the contest. ... The contrast Walker effectively drove between the general direction of the state and that of the city of Milwaukee played into fears/doubts/dislikes that many people already had."

The burden of "mayorhood" among those who aspire to the governorship is far from unique to Barrett. Take New York Mayor Ed Koch. In 1982, he lost a Democratic gubernatorial primary to Mario Cuomo. Kevin White of Boston failed to win the governorship in 1970, as did Martin Chavez of Albuquerque in 1998. John DeStefano, the mayor of New Haven, failed to unseat an incumbent Republican governor in Connecticut. In 2010, San Francisco Mayor Gavin Newsom pulled the plug on a gubernatorial campaign; no San Francisco mayor has won the governorship since Republican James (Sunny) Rolph in 1934. Los Angeles mayors of both parties -- Sam Yorty, Tom Bradley and Richard Riordan -- all failed in bids to become governor of California, with Bradley losing twice.

Of course, there are the big-city mayors who, sensing long odds, decided against running statewide in the first place. Koch, for instance, is the only 20th-century New York City mayor to have even made a gubernatorial run. Since Michigan became a state in 1837, only two Detroit mayors have made the leap to governor.

Ed Rendell is the only Philadelphia mayor to win the governorship of Pennsylvania since the dawn of the 20th century, and only one Pittsburgh mayor won the governorship during the same period. In Boston, the last mayor-turned-governor was the notoriously corrupt James Michael Curley in the 1930s.

Historically, then, the hurdles arrayed against mayor becoming governor are substantial -- and it's not hard to see why. In many cities social and economic problems have become intractable, with some suburbanites and rural residents feeling disconnected from, and often fatigued by, the urban challenges mayors tackle. Meanwhile, residents of far-flung parts of the state may harbor resentments against the big city, whether justifiable (over the division of budgetary resources in the state, for instance) or simply due to ancestral biases.

"When we went after Riordan in the 2002 GOP primary," said California-based Democratic operative Garry South, "our polling and focus groups picked up a lot of resistance and resentment toward a mayor of L.A. running for governor, and not just among working-class voters in places like the Central Valley, but also among highly educated professionals in the Bay Area."

In addition, being able to connect with a diverse and liberal-leaning urban electorate doesn't necessarily translate into the ability to connect with moderate-to-conservative voters elsewhere in the state, particularly if a mayor needs to flip-flop on policy stances in order to run statewide.

At the same time, though, there's been a bit of a turnaround in mayoral fortunes in gubernatorial races since the 2006 elections (when I first noted these trends in a column for Roll Call).

In the ten biennial electoral cycles between 1986 and 2004, nine mayors won the governorship, of which six went on to win a second term. That's a rate of less than one new mayor winning per cycle.

But during the last three cycles, that rate has nearly tripled. Seven mayors won the governorship for the first time during that span -- Democrats Martin O'Malley in Maryland, John Hickenlooper in Colorado and Dan Malloy in Connecticut, and Republicans Sarah Palin in Alaska, Bill Haslam in Tennessee ,Paul LePage in Maine and Independent Lincoln Chafee in Rhode Island. The streak could yet continue: Later this year, Republican Pat McCrory, a former Charlotte mayor, is a modest favorite to win the governorship of North Carolina.

Political observers in these states suggest that the more recent crop of mayors-turned-governors has avoided some of the pitfalls that hampered many of their predecessors. For starters, many of the newest crop served as mayors of mid-sized cities that weren't as off-putting to voters elsewhere, such as Wasilla, Alaska (Palin), Stamford, Conn. (Malloy), Waterville, Maine (LePage) and Warwick, R.I. (Chafee).

Malloy's tenure as mayor of Stamford was "a major plus," said Ron Schurin, a University of Connecticut political scientist. In Connecticut, "the cities are viewed as dens of corruption, with lots of mayors now or recently in jail," he said. But Stamford is "partly suburban, has a lively economy, has a lot of affluent people in and around it and cultural attractions to match."

And in Maine, LePage, a veteran private-sector CEO, was able to tout his experience as part-time mayor of a Democratic-leaning city as evidence that he could bring business-style leadership principles to the challenges of government.

Even the mayors of big cities who won the governorship over the past three cycles appeared to be less burdened by their mayoral records. As any viewer of HBO's The Wire knows, O'Malley could have been tarred by any number of problems emanating from Baltimore. Yet in his first race against Republican Gov. Bob Ehrlich, the issue "had no effect that I could tell," despite Ehrlich's efforts to bring it up, one Maryland Republican said. "Baltimore is not well regarded around the state, but people seemed to give O'Malley a pass on the city's problems."

In Colorado, Hickenlooper's tenure in Denver was "a net plus," said Colorado State University political scientist John Straayer. "He had wide name recognition across the state and was broadly popular in substantial measure because of his relaxed and often humorous persona."

One of the biggest challenges facing a candidate like McCrory, the former Charlotte mayor now seeking the North Carolina governorship, is how to reconcile past issue stances on hot-button issues with those expected by a statewide electorate.

"For some of the city's initiatives, especially around building light rail, tax increases occurred under his watch," said Jonathan Kappler, research director for the pro-business North Carolina Free Enterprise Foundation. "That wasn't really a problem for Charlotte voters, but could be a problem with some general election voters, especially in rural parts of the state."

McCrory could take a page from Haslam, the former mayor of Knoxville. He's managed to appeal to both moderate and conservative voters in Tennessee. Initially a moderate technocrat, Haslam "tacked right" when it became "obvious that he had higher ambitions," said University of Tennessee political scientist Anthony Nownes.

As governor, Haslam has maintained his popularity since winning office in 2010. He's "regarded as a solid, hard-working, reasonable guy," Nownes said. "He forged that image here in Knoxville, and it has remained with him."

In fact, despite the historical obstacles to mayors winning the governorship, they do tend to bring some of the best possible experience to the job when they do manage to win. Being a mayor means serving as the top executive responsible for such policy areas as law enforcement, education, public infrastructure and business development.

"Mayors are uniquely equipped for the challenges new governors face," said one Democratic strategist who's worked in mayoral and gubernatorial administrations. "They've had the opportunity to submit and govern within a budget. They've had to work with a legislative body that has their own perception of who controls government. They've managed departments. It's not a perfect translation, but that experience shortens the learning curve."