Hillary Clinton, who is expected to jump into the 2016 presidential election soon, got loud cheers at a speech in Washington, D.C. when she played to suggestions that she will officially run for the White House. (Reuters)

A top adviser to Agriculture Secretary Tom Vilsack, a former Iowa governor, is leaving the Obama administration to manage Hillary Rodham Clinton's likely presidential campaign in Iowa, four Democrats familiar with the move said Wednesday.

Matt Paul, an operative with more than two decades of political experience in Iowa, will return to the Hawkeye State to oversee Clinton's campaign for the first-in-the-nation caucuses, said the Democrats, who requested anonymity because they were not authorized to discuss the move.

A senior adviser to Vilsack since his 1998 gubernatorial campaign, Paul currently serves as director of communications at the U.S. Department of Agriculture. Paul announced his resignation on Wednesday and plans to depart by the end of March, said a USDA official, who requested anonymity to speak about Paul’s plans.

Other experienced Democratic operatives are in serious discussions to join Paul on the likely Clinton Iowa campaign staff.

Lily Adams, currently deputy communications director at the Democratic National Committee and a former aide on Sen. Tim Kaine's 2012 campaign in Virginia, is poised to fill a top Iowa communications job for Clinton, according to a person familiar with the discussions.

Brenda Kole, who served as a senior adviser on Jack Hatch's Iowa gubernatorial campaign in 2014 and before that was director of advocacy and organizing for Planned Parenthood of the Heartland, is slated to take a top political role on the Iowa team, the source said.

The Clintons and the Vilsacks have long and deep ties, their relationship having been described almost as family. Hillary Clinton worked with Christie Vilsack’s brother on the staff of the House Judiciary Committee during the Watergate impeachment investigation.

When Tom Vilsack ran for governor in 1998, Clinton appeared on his behalf at a fundraiser, which Vilsack recalled as one of the turning points in that campaign. Clinton also helped during his reelection campaign.

As governor of Iowa, Vilsack looked to Bill Clinton for advice on how to be a governor after he was elected. The two are policy wonks in addition to being politicians.

In addition to working with Vilsack, Paul also served as deputy Iowa state director for Howard Dean's 2004 presidential campaign. He has close ties to retiring Sen. Tom Harkin, the state's most senior Democratic officeholder, having worked as campaign manager for Harkin's 2008 reelection.

Paul began his career as a journalist, working as a television and radio reporter in Cedar Rapids, Iowa, before moving into politics in 1994 to serve as spokesman to then-Mayor Larry Serbousek.

The appointment of Paul comes as Hillary Clinton -- the overwhelming favorite for the Democratic nomination -- is building out a campaign team ahead of her official launch, which is expected to come as early as April.

Clinton has filled many senior positions at national headquarters, likely to be in New York, including John Podesta as campaign chairman, Joel Benenson as chief strategist and Robby Mook as campaign manager. Clinton now is beginning to recruit staff in key states such as Iowa, where she struggled in her 2008 campaign and finished third in the caucuses behind Barack Obama and John Edwards.

Hillary Clinton acknowledged Sen. Barbara Mikulski (D-Md.) and EMILY's List founder Ellen Malcolm for their advocacy work for women's rights during her acceptance speech at the organization's 30th anniversary gala. (AP)

Update:

In a statement, Vilsack praised his departing aide:

"Matt Paul has been a close friend and advisor to me for nearly 20 years. Since he joined my team as Governor of Iowa in 1998 and throughout our work together at USDA, Matt has demonstrated a fierce commitment to public service, especially to serving those living in rural America. Matt believes in improving the efficiency and effectiveness of government through clear and compelling communications, and he has proven that here at USDA by integrating and modernizing our outreach and branding, helping to build a stronger digital platform, prioritizing stakeholder engagement, and elevating the voices of American citizens and businesses in all that we do. I deeply appreciate his service and friendship, and I wish him all the best in his future endeavors."