"I congratulate Bill on his victory over a capable, dedicated and tenacious young opponent ... but the Republican primary was merely a battle between two men with similar agendas," Politis, 55, said in a statement Wednesday.
"Today we begin the campaign of real alternatives and real choices for the future of our 15-county community known as the 9th Congressional District and our larger community, the United States of America," he said.
Politis, of 56 Homestead Drive, Greencastle, polled 25,790 votes in the primary.
Politis and Shuster will face off in the Nov. 2 general election.
Six years ago, Politis announced he intended to run against another Shuster, Bill's father. In 1998, supporters of Bud Shuster filed a challenge to Politis' nominating petition with the Federal Election Commission. The challenge, Politis said in February, questioned the validity of many of the approximately 1,200 signatures.
Faced with the possibility of huge legal bills to fight the challenge, Politis said he decided to withdraw.
Bud Shuster resigned from Congress in 2001 and his son, who owned a car dealership, won the seat in a special election. Bill Shuster was elected to a full term in 2002.
The owner of an antique automobile manual and memorabilia business, Politis is the vice chairman of the Franklin County Democratic Committee.