FORT MADISON, Iowa (AP) — About 500 people packed into the basketball gym in the Fort Madison YMCA to see Mayor Pete Buttigieg in the working class Mississippi River town on the Sunday evening after Christmas. The following Sunday afternoon, Joe Biden attracted less than half to Grinnell, a similar sized college town in central Iowa.

On the surface, the larger turnout for the 37-year-old former South Bend, Indiana, mayor could be a sign of greater energy and support as the nearly yearlong campaign for Iowa’s first-in-the-nation 2020 caucuses reaches its final phase. Or not. The ritual, frenetic chase for momentum — an often illusory but essential element to winning Iowa — is on.

“Big Mo,” as George H.W. Bush called it after winning the Iowa caucuses in 1980, could allow one of a cluster at the top in Iowa including Buttigieg and Biden to break away in the final month, help another work his or her way into the pack or, just as easily, paint a target on someone’s back.

Buttigieg’s team points to crowds in Fort Madison and others that are several times the size of his rivals’ crowds as evidence he’s got it. Others stake their own claims. After a year of campaigning, whoever looks hot today could also be limping out of Iowa next month after the Feb. 3 caucuses.

The problem is knowing “what evidence on the ground is really the most dynamic and is going to be the most influential come caucus day,” said Democratic pollster Joel Benenson, a former adviser to Barack Obama and Hillary Clinton.

“I do think momentum can be real,” said Benenson, who has also helped Buttigieg. “But it depends on whether the campaign organization is actually building that momentum in the ways that will matter on Election Day in getting people to the polls, not just getting them to town halls and events.”

Buttigieg’s campaign aides argue that proportionally larger audiences across the map, especially last week in small towns in southern and eastern Iowa, are signs of higher interest in him than in his rivals in the critical ramp-up to the leadoff nominating contests.

Minnesota Sen. Amy Klobuchar, an Iowa neighbor projecting herself as a pragmatic Midwesterner, touted the spike in her financial contributions after a debate last month as a sign she’s on the move, with money to invest in all-important organizing in Iowa.

Likewise, flush with the field’s biggest fundraising quarter, Vermont Sen. Bernie Sanders’ team is predicting he will win Iowa.

Crowd sizes, however, are not always proxies for support. It often takes more than a late infusion of cash to assemble an aggressive statewide organization, and fundraising success doesn’t always translate into the political apparatus needed to deliver support to the caucuses. Fluidity in the race, especially the last month in Iowa, is the norm.

Take Howard Dean, who drew big crowds and robust fundraising in the fall of 2003, having excited frustrated Iowa Democrats by railing against a 2004 Democratic field dominated by members of Congress who had voted to authorize the use of force in Iraq a year before the war became overwhelmingly unpopular among party activists.

Dean, despite his fiery indictment of President George W. Bush, came under attack from rivals concerned that Dean, the former governor of Vermont who had no national security experience, would lose to the well-financed, wartime Republican incumbent, and he fell sharply to third place over the final weeks before caucus day.

“My experience has been momentum is not necessarily a great thing going into the caucuses,” said Joe Trippi, Dean’s 2004 campaign manager. “The people I would not want to be right now, or who face a big hurdle, are Pete and (Massachusetts Sen. Elizabeth) Warren because I think those kinds of doubts end up eroding their support in the next month.”

In 1988, Missouri Rep. Dick Gephardt, having moved his family to Iowa the previous summer, leaped into the lead in the closing weeks of that year’s crowded caucus field, seizing on labor anger with foreign manufacturing competition and farmers grappling with a vicious credit crisis. He ended up winning the Iowa caucus that year but losing the Democratic nomination.

Sixteen years later, Gephardt would implode in a comeback effort, tangling with Dean during the closing weeks, allowing Massachusetts Sen. John Kerry to quietly rise and win the 2004 caucuses.

And the instability in the Middle East, accelerated by President Donald Trump’s order to have Iran’s top general Qassem Soleimani killed last week, could provide a boost for Biden, the former vice president, who claims the field’s most far-reaching foreign policy experience.

Hillary Clinton famously moved into the lead in Iowa in the fall of 2007, only to be surpassed in the closing two months by fast-rising star Barack Obama, who won the caucuses en route to the nomination and White House.

Obama’s success was fueled by an influx of first-time caucus participants, an element Buttigieg’s campaign is working to replicate. The Des Moines Register’s November Iowa poll showed 30% of likely caucus participants expected to attend for the first time, on par with the 2008 campaign at the time.

Similar polling nuggets can provide clues to who has the juice heading into the final stretch. But some hints of movement are evident at the increasing number of campaign events around the state or organizing efforts in neighborhoods where campaign volunteers are knocking doors and engaging voters face-to-face — or not.

Despite plateauing in Iowa polls after a summer surge, Warren, whose campaign is well organized in the state, has shown signs of durability, even as she has come under fire from Buttigieg and Klobuchar for an array of plans that would rely on a controversial wealth tax to accomplish.

Julie Jutte attended a recent Warren event on a snowy Monday in small-town Keokuk, leery that the senator could accomplish her breadth of plans, including debt-free college and universal, government-financed health care.

Like others who ventured out to see Warren for the first time on a recent southeast Iowa trip, the 59-year-old Jutte, who cares full time for her aging mother, entered the union hall a skeptic and left a supporter.

“I’m all in,” Jutte said. “She convinced me.”

After battling Clinton to a near tie in the essentially two-way 2016 caucuses, Sanders remains a top 2020 contender in Iowa, where senior advisers have said recently they expect him to win.

And while Sanders posted the field’s best quarterly fundraising total this month — $34.5 million — Democratic Party officials in key counties say they see little evidence of the on-the-ground organizing required to net voters at these precinct-level, organizational-heavy contests.

“That is a stealth bunch,” Tom Courtney of Burlington, the Democratic county chairman in Des Moines County, said of Sanders’ local organizers. “You don’t hear much or see much of them.”

There are similar observations in Dallas County, in Des Moines’ burgeoning western suburbs, where the number of Democrats has grown faster than any other of Iowa’s 99 counties.

“I couldn’t even tell you who their staffer is in Dallas County,” said county Democratic Chairman Bryce Smith, who recently endorsed New Jersey Sen. Cory Booker.

In the end, it’s the momentum coming out of Iowa that matters more, Trippi and Benenson said. Winning Iowa, or finishing far better than expected, can help a candidate shake doubts that shadowed him or her in the months leading up.

“Momentum going into Iowa tends to create doubts, and momentum after Iowa, created by Iowa, overwhelms those doubts,” Trippi said.