The nonprofit arm of Crossroads is facing an Internal Revenue Service review that could eviscerate its fund-raising. Data projects nurtured by Mr. Rove are being supplanted in Republican circles by a more successful initiative funded by the Koch political network, which has leapfrogged the Crossroads organizations in size and reach.

And the group faces intense competition for donors from a new wave of “super PACs” that are being set up by backers of the leading Republican candidates for president, who are unwilling to defer to Mr. Rove’s authority or cede strategic and fund-raising dominance to the organizations he helped start.

In recent weeks, Crossroads has begun carving a niche for itself in attacking Hillary Rodham Clinton, the presumed Democratic front-runner. The group will use polling data and opposition research to paint her as “a typical politician who would say or do anything to get elected,” said Steven Law, president of Crossroads.

If the group’s role seems diminished, Crossroads officials are not complaining publicly. If anything, they are lowering expectations for an organization that raised $300 million in the 2012 cycle.