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(CNN) —  

The pilgrimage of all the leading 2020 Democratic contenders to Des Moines this Friday for a state party dinner testifies to the outsized influence Iowa continues to wield in the presidential nominating process. The paradox is that the candidates’ focus on Iowa is increasing even as the state’s odds of predicting the nomination’s winner may be shrinking.

In every contested Democratic nomination race in this century, the winner of the Iowa caucuses has eventually won the nomination. That’s a measure of how much momentum candidates can earn, especially in this era of pervasive news coverage, from winning that kickoff contest. Conscious of that history, the leading 2020 candidates have courted Iowa more aggressively than any other state on the primary calendar, whether measured by time, money or staff.

But the increasing diversity of the Democratic electorate – compounded by the unique racial dynamics of this race – raises the prospect that the 2020 contest could end Iowa’s winning streak in predicting the eventual nominee. The reason is that while it’s eminently possible to win Iowa, a virtually all-white state, without appealing to black or other minority voters, it’s almost impossible to win the nomination without cross-racial appeal.

For that reason, some Democrats are looking to South Carolina, a heavily African American state that votes fourth on the primary calendar, as a better gauge of how the race will ultimately unfold than either Iowa, which votes February 3, or New Hampshire, which follows with the first primary eight days later.

“While I think Iowa is a good place to get your feet wet, New Hampshire is a good place to get your feet wet, South Carolina is a place where you dive in the political pool and really start to swim,” says Antjuan Seawright, a South Carolina-based Democratic strategist who is uncommitted in the race. “It is the state that will ultimately decide who the next nominee will be.”

The predominant role that Iowa and New Hampshire play in the nomination process has generated internal party tension for years because the Democratic electorate in each state remains about 90% white, in a party where as much as 40% of the primary voters across all the states may be nonwhite.

But the impact of that racial contrast has been muted in the party’s four contested nomination races since 2000 for one big reason: The winners of the Iowa caucuses all performed well with black voters in subsequent states, particularly Al Gore in 2000, Barack Obama in 2008 and Hillary Clinton in 2016. (John Kerry, the 2004 Iowa winner, ran well, but not as dominantly, among African American voters.)

This year, though, polls point toward a heightened possibility of a divergence between the mostly white Iowa electorate and the more diverse states that follow.

Support among African Americans

Sen. Elizabeth Warren of Massachusetts has established a significant advantage in almost all state and national polls among white voters with college degrees, and in some surveys she’s turned in very competitive showings among white voters without college degrees as well. That pattern of support has pushed her into the lead in some recent Iowa surveys. Given the strength of the organization she’s built in the state, some local observers now consider her a clear favorite.

“Today I would say it is going to be really hard to displace Elizabeth Warren,” says Jeff Link, an Iowa-based Democratic consultant who is unaffiliated in the race. “She has not had a meteoric rise, she has had a slow and steady rise. She’s got a big organization and they are smart and they are doing stuff all over.”

But Warren has seen little support in polls among black voters, who cast about one-fourth of all the 2016 Democratic primary votes, according to a cumulative CNN analysis. That’s not a problem for her in Iowa – or New Hampshire – but it looms as a critical hurdle in the more diverse states that vote later, starting with Nevada and especially South Carolina. Sen. Bernie Sanders of Vermont and South Bend, Indiana, Mayor Pete Buttigieg, who appear positioned along with Warren to perform well in Iowa, also have registered little support with black voters – in Buttigieg’s case virtually none). Among the top tier of current Iowa contenders only former Vice President Joe Biden has displayed a consistent appeal for African American voters in polls.

That pattern heightens the possibility that Iowa’s streak of picking the party winners might end next year. The biggest question remaining in the 2020 race, in fact, may be whether a disappointing showing for Biden in Iowa – and possibly New Hampshire, too – will cause large numbers of black voters in later states, especially South Carolina, to move away from him.

“I don’t think it’s going to have any impact on the decisive vote in South Carolina, which is African American voters,” says Seawright. Iowa’s ultimate effect on the nomination fight could turn on whether he’s right.

Iowa and New Hampshire’s impact only grew in 21st century