Santorum told CNN's "State of the Union" Sunday Medicare and healthcare reform in general were necessary topics of debate.
"I think it is pretty clear that the central issue in this campaign right now, and I think will be going forward because it is a big issue, is Medicare," said Santorum.
The GOP has made the repeal of so-called Obamacare a major goal for Congress next year and convincing voters they have better ideas on healthcare will be critical to putting the necessary players in place on Capitol Hill and in the White House.
Santorum said presumptive Republican presidential nominee Mitt Romney was not plotting any complex cuts to the popular program but was seeking to expand some already-tested reforms.
"Twenty-five percent of seniors last year were in Medicare Advantage, which is a private sector health system within Medicare," Santorum said. "All he wants to do is to basically take that system to expand it so everybody has that opportunity. This is not a radical reform; this is exactly how the Medicare prescription drug program is run. Seniors like that program now."
Stephanie Cutter, deputy campaign manager for President Obama, said the Republicans were actually more bent on repealing the administration's steps to reform Medicare, which she said were working. "If Mitt Romney and Paul Ryan get elected to the White House, Medicare will be bankrupt by the end of their first term."