Hillary Clinton in Iowa amidst 2016 speculations

The former Secretary of State is appearing at a fundraiser, laying groundwork for a potential presidential campaign.

With speculation on a White House run in overdrive, Hillary Rodham Clinton returned to Iowa Sunday to pay tribute to the state's retiring Democratic senator as anticipation builds over the possibility of another presidential campaign.

Clinton and her husband, former President Bill Clinton, were to headline Sen. Tom Harkin's annual steak fry fundraiser in rural Indianola. Sunday's event was expected to draw more than 5,000 party activists who form the backbone of Iowa's presidential campaigns every four years.

Following a summertime book tour, Clinton was making her biggest campaign splash in 2014 so far, opening a fall of fundraising and campaigning for Democrats who are trying to maintain a Senate majority during President Barack Obama's final two years. The event was serving as a farewell for Harkin, a liberal stalwart and former presidential candidate who is retiring after four decades in Congress.

Obama defeated Clinton in the state's leadoff presidential caucuses in January 2008, and the former secretary of state has not returned since. Iowa Democrats said Clinton remained widely popular and predicted she would receive broad support if she chooses to run again.

"Barack Obama was a phenomenon. He just was. I'll give him credit, he worked hard in Iowa, but so did she," Harkin said, when asked whether Clinton would do things differently in the state if she runs in 2016.

On Sunday, party activists streamed onto a hot-air balloon field lined with colorful signs thanking the Harkins and promoting state candidates like Rep. Bruce Braley, who is running for Senate. Ready for Hillary, a super PAC supporting a potential Clinton candidacy, posted light blue "Ready" signs to promote the main speaker. On stage sat a quintessential Iowa tableau: bales of hay, an American flag and two tractors parked in the surrounding field.

"I honestly believe she will be the next president," said Cindy Sturtz, a union member from Fort Dodge, who caucused for Obama in 2008 but says she plans to support Clinton if she runs again.

The Clintons' arrival offered the possibility of a fresh start for the former New York senator and first lady, whose campaign stumbled in the months leading to the caucuses.

Anti-war activists opposed her vote to authorize the Iraq war in 2002 and coalesced around Obama, who had opposed the war as an Illinois state senator. Clinton was often insulated by a large entourage in a state where face-to-face politics has long been a campaign hallmark.

Clinton, who has conferred with Iowa Democrats in recent days, would enter a presidential campaign with a large advantage over potential rivals. Early polls have shown her leading other Democrats by wide margins, including Vice President Joe Biden and Maryland Gov. Martin O'Malley.

Biden is traveling to Des Moines next week and has not closed the possibility of another campaign while O'Malley has made several visits to the state and dispatched staffers to Iowa this fall.

Vermont Sen. Bernie Sanders, an independent who is considering a presidential campaign, said in an interview with NBC's "Meet the Press," that there was "profound anger at the greed on Wall Street" and at the nation's political establishment. Sanders said "the issue is not Hillary" but the decline in middle-class standard of living and the gap between rich and poor. "The American people want change," he said.

Harkin's final steak fry was expected to be the largest since Hillary Clinton's last appearance in 2007, when she was joined by Obama, Biden and other Democrats running for president. Bill Clinton has appeared at the event three previous times.

Clinton has said she expects to decide on another campaign early next year.