MOUNT VERNON, IOWA - APRIL 14: With crowds of supporters waiting for her, Secretary Hillary Clinton stopped at a coffee house in Mount Vernon, Iowa on Tuesday, April 14, 2015. (Photo by Melina Mara/The Washington Post)

This story has been updated.

Guy Cecil, a top Democratic strategist with close ties to Hillary Rodham Clinton, is poised to take on a major leadership role at the pro-Clinton super PAC Priorities USA Action, a move designed to send an unequivocal signal that Clinton wants donors to rally around the independent group.

Cecil, a seasoned field operative who served as political director of Clinton’s 2008 presidential bid, is in final talks to join the organization, a move that would diminish the role of board co-chair Jim Messina, according to two people familiar with the negotiations.

Messina, who served as President Obama’s campaign manager in 2012, will likely remain on the board in an active advisory role, according to the person, who noted that several details still need to be worked out. It is unclear what role Messina’s current board co-chair, former Michigan governor Jennifer Granholm, will play in the new configuration. But she is viewed as a valuable ally by Clinton advisers and may take on an active role with the campaign.

Buffy Wicks, who serves as the super PAC’s executive director, is expected to stay on. Cecil’s new role is expected to be finalized in the coming week. He will likely not be a full-time staffer, but rather function as the group's senior strategist.

A spokesman for Priorities USA declined to comment, as did Cecil. Messina could not be immediately reached.

The shake-up is being driven by concerns among Clinton advisers that the group needs to be led by a close ally who has been embedded in the former secretary of state’s political world and will be able to anticipate the needs of the campaign.

While super PACs are not allowed to coordinate strategy with candidates, the independent big-money groups are increasingly functioning as extensions of the official campaign operations. Former Florida governor Jeb Bush has devoted the last several months to raising tens of millions for his super PAC, Right to Rise, which is expected to be run by Mike Murphy, one of his top political advisers.

“When you look at what Jeb Bush is doing, everybody knew super PACs were going to be important, but that took it to a whole new level,” said one person familiar with the Priorities discussions.

While Messina is viewed as one of the party’s savviest strategists, he is not a Clinton intimate. Having Cecil in a top job at the super PAC would make it clear that the enterprise is sanctioned by her circle. Cecil, who most recently served as executive director of the Democratic Senatorial Campaign Committee, is close to both Clinton and her husband, former President Bill Clinton. His former colleagues from the consulting firm Dewey Square Group, Charlie Baker and Minyon Moore, are both set to play influential roles in Clinton’s 2016 campaign.

During Cecil’s time at the senatorial committee, he got to know some of the party’s biggest contributors, relationships that could prove extremely valuable in his new post. While Priorities has seen its fundraising pick up in recent weeks, the super PAC lags far behind the Bush group.

The massive sums that Bush has been stockpiling in his super PAC have alarmed Clinton personally, according to people familiar with her sentiments. And they have driven home the need to ramp up fundraising for Priorities USA. The super PAC, which was originally launched to back President Obama’s reelection, was refashioned into a pro-Clinton vehicle by supporters such as DreamWorks Animation chief Jeffrey Katzenberg. But because Clinton has not yet made it clear she wants supporters to write big checks to the group, Priorities has had a rougher time pulling in large sums than similar outfits supporting candidates on the right.