Iowa is small but it kicks off the quadrennial race for the leader of the most powerful nation in the world.

Iowa is in the middle of America’s heartland and every four years it is the epicenter of American politics. Iowa may not be the state of stage and screen fame where the “corn grows as high as an elephant’s eye,” but there is a lot of corn in the state and there are many more presidential candidates campaigning there than in Oklahoma.

Corndogs and candidates. Silly things and serious things. Deep-fried turkey on a stick and economic agendas for rural America. It was all there at the Iowa State Fair in recent weeks.

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Just about every Democratic presidential candidate made the trek to the state fair as did the political media. It’s a wonder there was any room for Iowans.

Attendance at the fair gave the Democratic hopefuls the chance to tour the state that is the first in the nation to choose delegates to the Democratic National Convention. It also provided the candidates the opportunity to criticize President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE for his trade policies they said hurt farmers and to release their own platforms for rural economic development.

In most states, the presidential campaign is an afterthought but in Iowa it’s the real thing. Democratic aspirants were as thick as flies in the summer heat in Iowa and many Iowa Democrats have already met the candidates. My guess is that many Oklahoma Democrats are only dimly aware there is a race for president.

Because of the visibility of the candidates there, polling in the Hawkeye State means more than the national polling. The state of public opinion there could be telling for the rest of the nation.

The big news out of Iowa is the rise of Sen. Elizabeth Warren Elizabeth WarrenOvernight Defense: Appeals court revives House lawsuit against military funding for border wall | Dems push for limits on transferring military gear to police | Lawmakers ask for IG probe into Pentagon's use of COVID-19 funds On The Money: Half of states deplete funds for Trump's 0 unemployment expansion | EU appealing ruling in Apple tax case | House Democrats include more aid for airlines in coronavirus package Warren, Khanna request IG investigation into Pentagon's use of coronavirus funds MORE (D-Mass.). A new online poll (with a margin of error of plus or minus 3.9 percent) conducted for Iowa Starting Line shows that she leads the field with 28 percent of the vote.

Former Vice President Joe Biden Joe BidenFormer Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick Bloomberg rolls out M ad buy to boost Biden in Florida MORE and Sen. Bernie Sanders Bernie SandersSirota reacts to report of harassment, doxing by Harris supporters Republicans not immune to the malady that hobbled Democrats The Hill's Morning Report - Sponsored by Facebook - Republicans lawmakers rebuke Trump on election MORE (I-Vt.) were tied for second at 17 percent. Sound Bend, Indiana Mayor Pete Buttigieg Pete ButtigiegBillionaire who donated to Trump in 2016 donates to Biden The Hill's Morning Report - Sponsored by Facebook - GOP closes ranks to fill SCOTUS vacancy by November Buttigieg stands in as Pence for Harris's debate practice MORE also registered in double digits at 13 percent, while Sen. Kamala Harris Kamala HarrisTexas Democratic official urges Biden to visit state: 'I thought he had his own plane' The Hill's Campaign Report: Biden on Trump: 'He'll leave' l GOP laywers brush off Trump's election remarks l Obama's endorsements A game theorist's advice to President Trump on filling the Supreme Court seat MORE (D-Calif.) clocked in at 8 percent. All the others were at 3 percent or less.

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Trump acknowledged the Warren surge when he said he would revive the controversial nickname he gave the Bay State senator a couple of years ago.

The trend in support for the Democratic candidates in the Iowa Starting Line poll is telling. While Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellDemocratic senator to party: 'A little message discipline wouldn't kill us' House to vote on resolution affirming peaceful transition of power Republican lawyers brush off Trump's election comments MORE (R-Ky.) has resisted bringing anti-gun legislation to the Senate floor in the wake of the El Paso and Dayton shootings, Warren has persisted and risen to the top of the Democratic heap.

Warren has surged big-time since May with a gain of 16 percent. Biden and Sanders who were leading the field in May were the big losers; each candidate lost 7 percent of their support.

These trends represent significant moments in the Democratic contest.

There’s a campaign within a campaign going on between Warren and Sanders for the championship of the progressive populist wing of the Democratic Party. It’s clear that Warren is winning.

Sanders’ standard stump speech given in Iowa has hardly changed from the speeches he gave there leading up to the 2016 caucuses. But his current level of support of 17 percent is far below the 44 percent mark he hit in the 2016 caucuses against Hillary Clinton Hillary Diane Rodham ClintonBloomberg rolls out M ad buy to boost Biden in Florida Hillicon Valley: Productivity, fatigue, cybersecurity emerge as top concerns amid pandemic | Facebook critics launch alternative oversight board | Google to temporarily bar election ads after polls close Trump pledges to make Juneteenth a federal holiday, designate KKK a terrorist group in pitch to Black voters MORE.

Voters don’t want the same old same old, and Warren offers caucus-goers a fresh perspective on the economic populism that the Green Mountain senator made so fashionable in the last presidential cycle.

The campaign in the center of the Democratic Party for leadership of the pragmatic liberal wing of the party is more muddled.

Iowans saw the best and worst of Biden. In Burlington, Iowa he gave a compelling speech on the need for a president who can heal the wounds of the nation after years of race-baiting by Trump. Then Biden stepped on his own moment in the sun with gaffes that clouded his message and made voters wonder whether he’s lost his fastball over the years.

Buttigieg performs better in Iowa than he does nationally, and he is close to Biden in the new survey. It could be that his effort to sell himself as the son of the Midwest is catching on. Harris is just out of double-digit range and it appears the surge she enjoyed after the first round of the nationally televised Democratic presidential debates has dissipated.

While Democrats hoofed their way through the cornfields and consumed cotton candy at the fair, Trump campaigned in the other small state, New Hampshire that has an outsized role in presidential politics.

Many political experts question the key role that small states like Iowa and New Hampshire play in presidential politics, but both states will be competitive in the fall of 2020. Trump won Iowa by 10 percent but his job rating is underwater in the Hawkeye State. Clinton won the Granite State by less than one-half of one percent.

Iowa may have only six votes in the Electoral College but those votes — and New Hampshire’s four — could make the difference in a close race. Especially when the president’s standing is shaky in the industrial Midwest that gave him his electoral-vote advantage in 2016.

There won’t be 20 presidential candidates at the Iowa State Fair next year, but there will be two candidates in attendance: Trump and the eventual Democratic nominee.

Iowa is important because it is one of many states that Trump won in 2016 but where his support is uncertain. If the president doesn’t win Iowa and states like it where he’s on thin ice, his tenure in the White House will end and his legal troubles will begin.

Brad Bannon is a Democratic pollster and CEO of Bannon Communications Research. He is also the host of a radio podcast “Deadline D.C. With Brad Bannon” that airs on the Progressive Voices Network. Follow him on Twitter @BradBannon.