And the party establishment is starting to take notice.
The nonprofit group based outside Harrisburg has spent hundreds of thousands of dollars since it was launched in 2009, and is gearing up to do so again this year.
It won't reveal its specific targets, but several Republican state representatives from the Philadelphia suburbs are on its list, Leo Knepper, CAP's executive director, said in an interview.
"What we want to do is keep voters informed," said Knepper. "There are a lot of representatives who will come home to their districts and say all the right things, that they are pushing for more limited government or to make government more fiscally responsible. Then, when these guys go back to Harrisburg, their behavior is directly at odds with what they've said."
The GOP party establishment sees it differently.
Many Republicans contacted by The Inquirer would agree to speak only on condition of anonymity, saying they did not want to incite CAP members, particularly since there is still time for the group to back primary challengers. This year, all 203 seats in the House and half of the 50 in the Senate are up for grabs.
They contend CAP is intolerant and unwilling to understand that compromise is a necessary component of the legislative process. They also seethe at the fact that the conservative group is registered under the tax code as a 501(c)4 group, a "social welfare" organization whose mission is not primarily political - and therefore does not have to disclose its donors.
"We have to disclose who gives money to our campaigns," said one Republican legislator who has been targeted by the group. "Why don't they? Who gives them money to do what they do?"
In interviews, CAP members said the group was founded by a small circle of people who believed that the Republican Party had begun straying too far from conservative and free-market ideals.
The group included former State Rep. John Kennedy, from Cumberland County, who became somewhat of a pariah in the legislature before he retired in 1988, because he advocated against legislative pay hikes and lawmakers' generous benefit and pension plans; and Matt Brouillette, who runs the right-leaning Commonwealth Foundation in Harrisburg. Brouillette is no longer with the group.
At the same time they launched the nonprofit, they created a separate political action committee for CAP, which over the last four years has spent hundreds of thousands of dollars on candidates. Knepper said that since 2012, CAP only supports candidates who agree to opt out of the state pension system.
On the political action committee side, campaign finance records show that CAP's most generous donors have included the pro-school voucher group Students First, launched by three wealthy suburban Philadelphians who founded Susquehanna International Group, a financial trading company in Bala Cynwyd; and York businessman Scott Wagner. Wagner is now running for a state Senate seat.
In 2012, Students First's political action committee gave CAP's political action committee a half-million dollars, according to records. Wagner, who runs Penn Waste Inc. in York, gave slightly more than $120,000 that year.
Knepper declined to disclose the donors to the 501(c)4, but said the majority of CAP's donors are from Pennsylvania, and that many of the people who give to the political action committee also give to the 501(c)4.
He also said the majority of CAP's spending on elections comes out of the PAC, but that it does use the 501(c)4 to bring attention to an issue or send mailers to voters in a specific legislators' district.
Rep. Jerry Knowles (R., Schuylkill) knows all about those mailers. He said CAP targeted him in 2012 and is doing so again this year when he faces a primary challenger.
"I am a very conservative guy," said Knowles. "I don't believe in litmus tests, but if there were one, you would see I vote on the right side of their litmus test every single time."
Knowles, a self-professed believer in school choice and right-to-work legislation, said residents in his district have received fliers from CAP about his pension - he contends they were misleading - and about votes he's cast on taxes.
Other Republicans targeted by CAP include Reps. Gene DiGirolamo of Bucks County and Tom Murt of Montgomery County. Unlike Knowles, DiGirolamo and Murt are considered moderate Republicans.
In 2012, CAP's work helped unseat former state Rep. Rick Geist of Blair County. Geist had chaired the House Transportation Committee and had pushed hard for a multibillion-dollar transportation funding bill, which some conservatives have eschewed.
And CAP this year has taken some credit for Smith's announcement late last month that he would not run for reelection. Smith faced a rematch with primary challenger who had nearly defeated him in 2012.
That, in fact, is what prompted the Republican House Speaker to push back against CAP. Smith sent the group a scathing letter late last month, blasting its members for "petty, potshot politics," as well as its "purist views," which he compared to those held by dictators.
He warned that the group's efforts will only lead to relegating Republicans, who now control the House, to the minority - "albeit a politically pure minority," he wrote. He urged them instead to go after those who disagree with their agenda: Democrats.
For his part, Knepper said CAP does mount election challenges against Democrats but noted the group "was born to create a level of pressure" on the Republican party to stay true to its ideals.
"If Republicans in Pennsylvania would act on the principles that they espouse, our organization wouldn't exist," he said. "The only reason CAP has a market is because the Republican Party here is failing to live up to its image."