WASHINGTON -- Not that long ago, Karl Rove emerged as a mastermind of a new type of campaign spending, leading a wave of outside groups whose ability to pour money into the 2010 midterm election helped Republicans gain control of the House and bolster GOP ranks in the Senate.
The former George W. Bush adviser's reputation as a strategist soared -- as did the often oversized caricature of him as a Republican boogeyman who could always be counted on to rattle the political left.
This midterm election cycle, though, is shaping up differently. Mr. Rove's two funding groups, American Crossroads, a super-PAC that discloses its spending, and Crossroads GPS, a nonprofit that does not, are playing more of a supporting role.
The new stars of the dark money circuit are the billionaire Koch brothers, whose Americans for Prosperity has funneled a jaw-dropping $35 million so far into the midterm election cycle, much of it spent even before the first primary ballots were cast this spring.
Mr. Rove's activity has paled by comparison. American Crossroads reported raising just $6 million in the first quarter of 2014, and both of Mr. Rove's groups recently announced plans to spend $9.3 million on summer TV ads in four battleground states: Arkansas, Colorado, North Carolina and Alaska.
That's a fraction of the $175 million his groups spent in the 2012 election, or the $72 million they spent in the 2010 midterm. (Verifying expenditures is difficult because much of the money does not have to be disclosed in a timely way, leaving watchdog groups to cobble together estimates from various sources and estimates, including TV ad buys.)
Part of the change may stem from a drop in contributions. Many conservative donors felt angry or disappointed over Mr. Rove's dismal performance in the last presidential race, when Mitt Romney lost and almost none of the congressional races went Mr. Rove's way.
The Sunlight Foundation, a campaign watchdog, suggested donors' "return on investment" from money they gave to Mr. Rove's groups was among the worst of 2012. In 13 congressional races that American Crossroads tried to sway, it succeeded in just two, the group found.
Although they may not be spending as much, the Crossroads groups are marshaling their resources more strategically in key states where operatives believe they can achieve the most bang for their buck. And they are getting results.
For example, American Crossroads swooped into the GOP primary election for Senate in North Carolina during the final stretch of the campaign to hoist Thom Tillis, the GOP establishment-preferred candidate, over a tea party-backed alternative. The race put Rove back on the national stage. But now it's one he shares with many others, largely Americans for Prosperity.
Despite Mr. Rove's late start this election, few are ready to count him out.
"I'm sure they're going to be back," said Bill Allison, editorial director at the Sunlight Foundation. "They can pour it on."