(ABC News)

GOP presidential candidate Rick Santorum said this morning that his previous support for former Pennsylvania senator Arlen Specter's presidential campaign for president in 1996 was a mistake.

"I was his colleague in the United States Senate. He asked me to stand with him. That certainly wasn't one of my prouder moments I look back on. But look, you know, you work together as a team for the state of Pennsylvania," said Santorum. "I certainly knew that Arlen Specter was going nowhere. I certainly disagreed with a lot of things that he said."

Santorum, who is fiercely against abortion, appeared on stage with Specter in 1995, who was vocally pro-choice at the time.

"I want to take abortion out of politics … and leave moral issues such as abortion to the conscience of the individual. That is a matter to be decided by women, not by big government," Specter said in 1995.

Santorum said his support for Specter hinged partially on Specter's support for him when he was running for office in 1994.

Supporting Specter "was something I look back on and wish I hadn't done," Santorum said.