Bill and Hillary Clinton plan to campaign and raise money for Sen. Mark Pryor’s re-election bid in Arkansas, a source with knowledge of discussions between the Clintons and Pryor’s campaign confirmed Wednesday.

The plans are still fluid, but the Clintons will “be involved and helpful whenever they (can) be,” the source said. Hillary Clinton’s level of involvement in particular will depend ”on her political schedule and when she decides to start dipping her toe in the political waters.”

The role of the former governor and first lady of Arkansas will likely include both public events and private fundraising on Pryor’s behalf. A spokesperson for Bill Clinton did not immediately respond to a request for comment.

Pryor, a Democrat, is facing a competitive challenge from Rep. Tom Cotton, a Republican, who in early surveys is running neck-and-neck with Pryor. The race is a critical one for Republicans if they are to retake the majority in the Senate.

But the Clintons, who are still regarded highly in Bill Clinton’s home state, would provide a major boost to Pryor in both fiscal and public-opinion spheres.

The Clintons have reason to pitch in: Their family has a longstanding relationship with the Pryors. Mark Pryor’s father, David Pryor, was Arkansas’ governor when Bill Clinton was still the state attorney general. In 2004, David Pryor became the first dean of the Clinton School of Public Service in Little Rock.