Super PACs backing GOP presidential primary contender Sen. Ted Cruz are reportedly ready to loosen the purse strings for the surging Texas lawmaker.Federal Election Commission records show the four primary pro-Cruz groups have been fiscally conservative up to this point, spending about $2.2 million of the $38 million raised in the first half of the year, The Wall Street Journal reports.And the Cruz campaign is happy with the strategy."There will come a time real soon where it's going to get real expensive fast," Rick Tyler, a Cruz campaign spokesman tells the Journal, which points out Tyler has no "inside knowledge" of the spending plans."It would be great to have a lot of money then."It isn't the path followed by the super PACs supporting rivals, including one backing poll-lagging Jeb Bush, which has spent nearly half of the $103 million it raised in the first half of the year, including $30 million on a TV ad blitz, the Journal reports.But even with the low-spending by Cruz-supporting super PACs, Cruz has had stellar Iowa polling results , and is sitting in second place behind Donald Trump in national polling averages. "The conventional model of super PACs is to collect check after check and then run ad after ad," Kellyanne Conway, who heads Keep the Promise I, a pro-Cruz super PAC, tells the Journal. "We didn't see that as the best way."The group has aired less expensive digital and radio ads, but plans to go with TV advertising next month, the Journal reports.Conway says the group is building "mini-campaigns" in early-voting states, and is "sitting on professionally produced, factually verified, lawyer-approved contrast ads with at least three to four other candidates," the Journal reports."So if we need to respond in kind to false accusations, rumors, lies and insults, we're ready," she said.Republican strategist Rick Shaftan, who founded a pro-Cruz group of his own that has spent $75,000 on radio and digital ads in early states, now plans to spend at least $70,000 more, the Journal reports. He says the Keep the Promise approach has turned out to be a good one."We're in a 500-lap race, and we're probably in lap 402 now," he tells the Journal. "I think they're looking down the road."Cruz's super PACs, all named a variation of Keep the Promise, are each financed by a different family, including that of hedge-fund billionaire Robert Mercer; the billionaire Wilks family of Texas, who made their fortune in energy fracking; and private-equity-fund founder Toby Neugebauer, the Journal reports.