Chicago Mayor Rahm Emanuel offered a surprise endorsement Friday for Hillary Clinton, should she run for president in 2016, while pledging his support to Ready for Hillary, a super PAC working to establish and expand a network of Clinton's supporters.

"Hillary is smart, she's determined, and most importantly, she is a champion for the American people," Emanuel said in a statement released by Ready For Hillary. "I'm proud to make my support for her official, and I'm even prouder to join more than two million Americans encouraging her to run."

Emanuel and Clinton worked together in President Obama's administration when he was chief of staff and she was secretary of state.

"I've seen firsthand how Hillary has inspired women and men, and girls and boys, here in America and across the globe," Emanuel continued, "and I know that as president, she would continue to move our country forward."

Emanuel is just the latest former Obama aide to pledge allegiance to a potential Clinton bid: Notably, former Obama campaign manager Jim Messina signed on early this year with Priorities USA, the former pro-Obama super PAC that has pledged to raise money for Clinton leading up to 2016.

But Emanuel has a history with the Clintons that stretches back decades, to when he directed Bill Clinton's finance committee during his first presidential campaign. When Clinton won the presidency, Emanuel was named as an adviser to the president.

Now, Emanuel will work to put another Clinton, Hillary, in the White House. Ready For Hillary announced Friday that Emanuel will headline two events for the group in Chicago on June 5, and Emanuel wrote a fundraising email for the group that was sent to supporters Friday.

Clinton, for her part, has acknowledged that she is thinking about running for president, but has said she doesn't plan to reach a decision imminently. Clinton will be kept busy in the meantime promoting her new memoir, "Hard Choices," to be released next month.