The latest national Democratic polls reflect an increasingly muddled national race with former Vice President Joe Biden trailed closely by Sens. Elizabeth Warren and Bernie Sanders.

But polls and recent reporting show a very different picture emerging in Iowa, the state that formally starts the nominating process next February.

Though in single digits in most national polls and state surveys, Mayor Pete Buttigieg has surged close to the top in Iowa, while Biden has dropped in some surveys from first to fourth. With 12 weeks until the Feb. 3 caucuses, substantial fluidity exists.

Because of Iowa’s potential to reshape subsequent contests, Buttigieg’s rise there has focused substantial attention on the 37-year-old South Bend, Ind., mayor, seeking to become the nation’s youngest president.

Since a well-received televised town hall last February, he has made an excellent impression, both in retail campaigning and in debates. His crowds, war chest and organized support have all grown.

But with increasing prominence comes increasing scrutiny of the attributes — positive and negative — Buttigieg would bring to a general election race against President Donald Trump and, beyond that, to the presidency.

First, his strengths:

He fits the profile of past Democratic presidential winners. Like Barack Obama, Bill Clinton Jimmy Carter and John Kennedy, Buttigieg is new, younger and an outsider. Candidates with those characteristics have consistently fared better than older insiders, like Hillary Clinton, Al Gore, Walter Mondale and Hubert Humphrey.

He’s smart. A Harvard graduate and a Rhodes Scholar, the South Bend mayor has shown command of the issues and an ability to define them, something that sometimes handcuffs the older, more experienced Biden.

He’s flexible. Initially, Buttigieg ran left, joining Sanders and Warren touting the controversial Medicare for all plan and urging drastic changes in the Supreme Court. Seeing Biden’s potential weakness, he moved to the center, exemplified by supporting a more incremental Medicare-for-all-who-want-it.

Intangibles. He is the only top candidate with military experience and, by all accounts, scandal-free. Biden has struggled to surmount fallout from his son Hunter’s controversial employment with a Ukraine energy firm.

Now, his handicaps:

He lacks national experience. For all of Mayor Pete’s smarts and grasp of the issues, he has never served in Washington, D.C. Being mayor of a city of 100,000 is hardly ideal preparation for the presidency. If elected, he’d be the fifth straight inexperienced president, though hardly as ill-prepared and unknowledgeable as Trump. The next president will need to start quickly to restore public trust.

Age. Buttigieg is six years younger than the youngest elected president, John F. Kennedy. But Kennedy had been in Congress 14 years when elected. So far, polls show more worry by voters about the age of some candidates than his youth.

His problems attracting African American votes. About one-fourth of all Democrats are black, and the proportion is larger in key primary states, starting with South Carolina. A recent New York Times/Siena College poll showed Buttigieg has minimal black support in those states.

More important, the African American voting age population is near or above the national average of 12.5% in general election swing states Florida, Michigan, North Carolina, Ohio and Pennsylvania. Democrats need a large, enthusiastic black turnout there to defeat Trump.

Three South Carolina focus groups convened by Buttigieg’s campaign found a significant explanation for black resistance was his sexuality — Buttigieg is openly gay and often appears with his husband, Chasten.

“Being gay was a barrier for these voters, particularly for the men who seemed deeply uncomfortable even discussing it,” concluded the Benenson Strategy Group.

“It was not necessarily a red line that they wouldn’t cross and many of the voters — particularly the older women —seemed genuinely intrigued by the mayor after hearing more. But their preference is for his sexuality not to be front and center.”

To “get past his sexual orientation,” the report added, “they are going to need to see real demonstrations of broad enthusiasm and likely some endorsements from ‘cool’ black people to help them believe that ‘other people’ don’t have a problem with it.”

“A lot of people my age feel that way,” one of the nation’s most prominent black politicians, South Carolina Rep. James Clyburn, said on CNN. But Clyburn, 79, called it a “a generational issue,” noting his grandson, Walter Clyburn Reed, is working for Buttigieg in South Carolina.

Still, even in Iowa, where a recent Times/Siena poll showed Buttigieg a close third, 55% of Democrats said they thought a gay candidate would have a harder time defeating Trump than other candidates.

Another problem: Buttigieg entered the race largely unknown in the national black community. Most rivals had campaigned there for years, and Biden benefits substantially from being Obama’s vice president.

“Our biggest barrier to black support is that Pete is a new face to Black America,” traveling press secretary Nina Smith tweeted. His campaign is sending black people from South Bend to validate him elsewhere.

Whatever the reason, no Democrat can win without maximizing black support. Mayor Pete still has a long way to go.

Carl P. Leubsdorf is the former Washington bureau chief of The Dallas Morning News and a frequent contributor.