Politico Magazine in July called it "The Suburb That Could Flip the House," so it's no wonder Pennsylvania's 8th District is one of several the Congressional Leadership Fund considers key to maintaining a Republican majority in the House. The super PAC recently said it plans to spend $10 million on what it considers competitive House races, many of which will also see an influx of Democratic dollars. The CLF, however, hopes its investment in analytics and voter data modeling gives it the upper hand when it comes to using its money efficiently.

The group is working with two Republican data firms -- Optimus and Deep Root Analytics -- to determine how best to target key voter segments and measure the impact of advertising on their likelihood to vote for a particular candidate. The two firms are each focused on different congressional districts.

Investing in data services "really matters in a congressional district probably more than it does in any other kind of race," said CLF President Mike Shields, the former chief of staff at the Republican National Committee who played a key role in the origin of the RNC's exclusive voter file provider, Data Trust.

"What's great about having Shields in charge of CLF is that he knows the Republican data structure better than anybody else because he helped set it up," said Alex Lundry, co-founder of Deep Root Analytics.

Deep Root and 0ptimus employ Rentrak TV viewing data along with other information on voters to help CLF optimize where and how it buys media. The firms help the PAC uncover which TV programs and channels its targeted voters watch in hopes of serving them ads in relevant and often relatively inexpensive ad slots. It's the modern approach to the more traditional reliance on spray-and-pray style TV buying methods that have resulted in ads being wasted on voters who are not part of the target audience.

"TV is one of their biggest weapons," said Mr. Lundry regarding CLF.

Starting Oct. 25, CLF will run $1.18 million worth of broadcast and cable TV spots and digital ads supporting Republican Brian Fitzpatrick in Pennsylvania's 8th district election. But the keystone state district is only one of several the group has in its sights; others are in Arizona, California, Colorado, Florida, Illinois, Iowa, Maine, Michigan, Minnesota, Nebraska, Nevada, New York, Texas, Virginia and Wisconsin.

Mr. Shields wouldn't reveal precisely how much the group has spent on data services, but he said CLF has spent "millions on our data back-end." Thus far, no expenditures with Deep Root or Optimus have appeared in Federal Election Commission filings from the PAC, though they are expected to show up in future reports.

In its work for CLF, Optimus has used information gleaned through surveys and other data to uncover how voters in each U.S. district compare or contrast. The company did something similar for Marco Rubio during his presidential primary run.

"In the races we are assigned we are taking a modeling and sampling process we developed in-house that allows us to make millions of phone calls to specific people on a continual basis and feed that data back into a modeling process to give CLF a holistic view of their races and target media resources accordingly," said Scott Tranter, partner at Optimus. "The end goal is to produce an entire picture across an entire map."

Each night, the company ingests data from 2 million phone call surveys which it processes and incorporates into its voter models, said Mr. Tranter, who believes data firms on the left take a similar approach. "The data comes back at midnight and there are answers at 7 a.m.," he said.

In an election year during which the presidential nominee's campaign may not help push the data analytics ball forward for Republicans, data investments by CLF and other groups could help the GOP keep up with data-centric Democrats. For instance, according to Mr. Shields, CLF works with GOP voter data provider Data Trust and incorporates voter scores and information it gathers back into that database, which is used by other right-leaning organizations.

The data-sharing practice is controversial, though. In 2014, Democratic group American Democracy Legal Fund filed a complaint with the FEC claiming that data updates added by super PACs to Data Trust's database and that of Republican data firm i360 constituted coordination because the information might be used by political parties and candidates. Campaign-finance laws forbid super PACs to coordinate with the actual political parties and candidates.

Mr. Shields suggested such complaints of data coordination were irrelevant and said the ADLF complaint has been dismissed by the FEC.