The fragmentation threatens not only the position of Mr. Rove and Crossroads as the dominant Republican players in the world of outside spending, but also the hundreds of millions of dollars’ worth of business that has flowed from Crossroads to a small circle of consultants and advertising buyers. In 2012, those consultants — many of them sharing the same floor of an office building in Alexandria, Va. — handled much of the media spending by the two Crossroads groups and Restore Our Future, a super PAC that spent $153 million to bolster Mitt Romney’s presidential campaign.

Mr. Law said Crossroads’ scale and its financial controls help maximize the amount of money that flows to actual advocacy. Because of the volume of advertising the Crossroads groups buy, they have been able to negotiate media buyers’ commissions down to 3 percent or less, far below the traditional rate.

Until recently, Crossroads’ deep ties to the Republican establishment were a source of authority and legitimacy, not controversy. Mr. Rove’s stature provided entree to prominent Republican donors around the country; Mr. Law and other officials there had long résumés with the party’s campaign committees, offering a kind of semiofficial imprimatur with donors and candidates.

But this year, Crossroads announced that it was financing a new effort, the Conservative Victory Project, to intervene in next year’s Republican primaries. Some conservative leaders accused Mr. Rove of trying to squelch anti-establishment candidates.

Now Crossroads appears to be testing a new approach. The group has so far stayed out of Kentucky, for example, where Senator Mitch McConnell, the minority leader, is facing both a Tea Party challenger in the primary and a strong Democratic opponent. Instead, Mr. McConnell is backed by a new group called Kentuckians for Strong Leadership. Although it is legally separate from Crossroads, most of its cash came from Crossroads donors, Mr. Law sits on its board, and the two organizations share a treasurer.

Crossroads has lobbied to help set up similar groups in races where its brand may be less appealing to voters or donors, according to two Republicans with knowledge of the conversations. But Mr. Rove has grown so controversial among some conservatives, the Republicans said, that candidates worry that donors will not contribute to a super PAC if it is connected to Crossroads.

In West Virginia, Mr. Law warned supporters of Representative Shelley Moore Capito, a Republican who is a top prospect to win a Senate seat next year, that if they formed their own super PAC, Ms. Capito would not be able to count on significant support from Crossroads, according to three people with knowledge of the discussions.