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Of all the men and women most commonly cited as top-tier 2016 presidential candidates, only one – Wisconsin Gov. Scott Walker – must first get through a costly and competitive 2014 election.

That makes Walker’s race different from the roughly three-dozen other campaigns for governor this year.

And it makes Walker’s presidential path a tricky and highly unusual one by modern standards.

Numerous politicians have used the office of governor as a launching pad for a national run.

But almost all of them in recent decades either left office before running for president (Mitt Romney, Mike Huckabee, Jon Huntsman, Tim Pawlenty, Howard Dean, Tommy Thompson, Lamar Alexander, Ronald Reagan, Jimmy Carter) or coasted through lopsided re-election races in advance of their presidential campaign (Rick Perry, George W. Bush, Bill Richardson, Mike Dukakis). Only Bill Clinton faced a real campaign test, but he still won re-election as governor of Arkansas by double-digits before making his White House bid in 1992.

Walker’s case is different. Even though he’s commonly favored to win re-election this fall, he is hardly a lock. In last month’s Marquette Law School poll, the GOP incumbent was tied with Democrat Mary Burke among registered voters — 46% to 46% — and had a slender three-point lead among likely voters.

One reason those results surprised some people in Washington is that it’s very odd to think of a widely touted presidential “aspirant” at risk of getting voted out of office by home-state constituents.

In 21 Marquette polls since 2012, the governor’s average approval rating is 49.5% and his average disapproval rating is 46%. His average “favorable” rating is 49% and his average “unfavorable” rating is 46%. That’s not a big cushion.

No one else’s 2016 prospects are more tied up in the 2014 election than Walker’s are (the most comparable case is that of Ohio Gov. John Kasich, who is also up for re-election but has generated less attention than Walker as a potential presidential candidate).

If Walker loses this fall, he has no presidential prospects. If he wins comfortably, his prospects are enhanced. And if he squeaks through by only a point or two, the results will be subject to a lot of spin. On the one hand, Walker could boast of winning three victories for governor in four years in a state that routinely votes Democratic for president. On the other, it would be an underwhelming kick-off to a national campaign. No sitting senator or governor in modern times has parlayed a narrow home-state election victory into a presidential nomination.

Walker’s 2016 ambitions also have implications for his 2014 race. The same uncompromising conservatism that made Walker a rising conservative star nationally has made him a polarizing figure in Wisconsin, kept him from expanding his political coalition in the state and ensured that even a politically unknown opponent could poll competitively against him in the months leading up to the November election.

There are inherent tensions between appealing to general election voters in a swing state and to the people that will determine the next GOP presidential nominee – Republican primary voters and activists, GOP donors, and conservative media.

Walker has threaded that needle so far -- an impressive political feat -- but it won’t get any easier between now and the November election.

Walker’s national ambitions could also play a direct role in the 2014 campaign. The governor has refused to pledge to complete a second term, and Democrats have argued that Walker is more focused on the next race for president than governing Wisconsin. History suggests those kinds of arguments don’t sway a lot of voters, but they could have an impact on the margins. Most governors who get attacked for their national travel, profile and ambitions don’t have competitive races at home to worry about. Walker is an exception to that. In Marquette’s last poll, 68% of independent voters said they did not want to see Walker run for president, and 66% said a governor can’t run for president and still handle the duties of governor.

Marquette’s recent surveys neatly capture Walker’s enduring strengths and weaknesses near the close of his first term.

Voters overwhelmingly see Walker as someone “who gets things done” but only a minority thinks he “cares about people like you.”

By 52% to 42%, voters think the state is heading in the right direction. But they overwhelmingly believe (with good reason) the state will fall short of Walker’s first-term promise of 250,000 new private-sector jobs.

There is virtually no evidence in the constant polling Marquette Law School has done that the state has grown any less divided over Walker since the recall, or that the governor has broadened his appeal. But the share of people who approve of the job he’s doing is almost always a little bit larger than the share of people who don’t:

The margins change from poll to poll, but the fundamentals don’t: the electorate is almost evenly divided; the governor is “favored” but not “safe.”

History suggests that’s a very unusual space for an “A-list” presidential hopeful to occupy.

Follow Craig Gilbert on Twitter @WisVoter