DES MOINES, Iowa (AP) — Hillary Rodham Clinton is returning to Iowa 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, are headlining Iowa Sen. Tom Harkin's annual steak fry fundraiser on Sunday, an event expected to draw more than 5,000 party activists.

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 hold onto a Senate majority during President Barack Obama's final two years.

The event in rural Indianola is serving as a tribute and farewell to Harkin, a liberal legislator and former presidential candidate. He's retiring after four decades in Congress.