Senate Minority Leader Mitch McConnell (R-KY) designated McCain as the front man for the leader's amendment in the first major debate for the biggest piece of legislation the chamber has seen this year.
"McCain has come back to the Senate fired up and is working hard," Don Stewart, a McConnell spokesman, told TPMDC.
"It was not a tough argument. McConnell wanted him out there and McCain has been eager to get out on this issue," Stewart said. "There a lot of people that pay attention to him."
Surveys show McCain has one of the highest name recognitions among senators in both parties.
"His Twitter page is much bigger than mine," Stewart said. (McCain has 1.6 million followers, Stewart has 548, many of them journalists.)
He added that senators are "having a lot of fun" debating the health care bill (follow our updates here) and Republicans like having McCain around after he spent nearly two years on the campaign trail.
Sen. Olympia Snowe (R-ME) lauded McCain on the Senate floor yesterday, calling him a "stalwart" in the debate.
A Republican staffer who worked for McCain in 2008 said the party spent "millions of dollars bolstering his national image," so it makes sense for him to be the go-to guy.
"Does anyone know who Mitch McConnell is?" the staffer asked.
Besides, the staffer said, Republicans trust they McCain can make clear cases against any Obama initiative since he spent a year doing just that.
Others said despite McCain's prominence on military issues, health care has always been in his bailiwick.
Former Congressional Budget Office Director Douglas Holtz-Eakin, who advised McCain on policy during the campaign, said the Senate's focus would be on health care if the Republican had won the presidency because he also had deemed it a top priority.
Even when others were advising he ignore the issue during the GOP primary, McCain "insisted we have a plan, he was constantly asking about health care reform," Holtz-Eakin told TPMDC.
Holtz-Eakin agreed that McCain has a higher national stature than other Senate Republicans.
"He came out of the campaign with the mantle of party leadership even though he didn't win the presidency," he said.
Former RNC staffer Alex Conant, now working for Minnesota Gov. Tim Pawlenty's 2012 effort, said McCain's engagement on health care is paying dividends.
"He's been very valuable to Senate Republicans who are seeking to raise the profile of this debate," Conant said.
When Sen. John Kerry (D-MA) returned to the senate after losing the 2004 presidential election, Senate Democrats did not embrace him in a similar way.
Kerry's charge against the Iraq war garnered little support and he wasn't looked to by leadership to speak for the party.
McCain is facing a primary challenge from the right in 2010, which has been one reason he's been more aggressive on going after both Obama and national Democrats.
Political hands from both parties say McCain has nothing to worry about, but that won't stop them from making the race seem top-tier to raise money and interest in a battleground state.
Late Update: We revisit the 2008 health care debate here.