On Capitol Hill, where the partisan divide runs so deep it has shut down the government, it can be unusual for members of opposing parties to publicly join together for much of anything -- much less birthday cake.
Yet there was Sen. Dick Durbin, the Senate's second-ranking Democrat, surprising Republican Sen. Mark Kirk with a sheet cake and a round of "Happy Birthday" following one of the breakfasts they regularly hold for constituents visiting Washington.
"I wanted to get one of those Annapolis sabers for you to cut the cake," Durbin told his fellow senator from Illinois, a former officer in the Naval Reserve.
Kirk smiled and quietly noted the significance of the milestone.
"I made it to 54."
The two senators have worked together cordially since Kirk won President Barack Obama's former Senate seat in 2010. But the relationship has gotten closer, and more public, since Kirk suffered a stroke last year that left some wondering if he would celebrate another birthday, much less return to the U.S. Senate.
The cross-party friendship is an uncommon sight, even in what's considered Washington's more decorous chamber. Some members -- Louisiana Sens. Mary Landrieu and David Vitter, for example -- have been known to spar openly. Other state senators of rival parties cooperate amicably on constituent issues. But few are as outwardly chummy as Durbin and Kirk, whose actions have even elicited a few eye rolls and wisecracks about a "bromance" from political observers.
Weeks after marking Kirk's birthday, Durbin praised him in a speech on the Senate floor. On Durbin's birthday, Kirk's office sent over cupcakes -- and then put a picture out on Twitter of the two of them together, laughing.
"Without naming names, there are states that couldn't pull this off," Durbin said. "And even some states with senators both from the same party couldn't pull this off."
The partnership has an expedient side. In many states it's almost a political necessity for elected officials of opposing parties to come out swinging to excite their party's most fervent loyalists. The rise of the Tea Party has only heightened that instinct.
But in Illinois, one of 17 states with split Senate delegations, Durbin and Kirk have clearly concluded the opposite plays better. Most statewide elections are decided by moderate voters in Chicago's suburbs, who have tended to switch between voting for Republicans and Democrats, and who could be put off by harsh partisanship.
Durbin, who is finishing his third term, is up for re-election next year, and Kirk has said he's running again in 2016 -- a seat Democrats already are jockeying to try to take back.
For Durbin, who earned a reputation as a staunch Obama ally while serving as assistant majority leader, the bipartisan vibe "gives him a little more middle-of-the-road narrative," said longtime Chicago political analyst Thom Serafin.
Durbin has recently touted other bipartisan efforts, such as his work with the so-called "Gang of Eight" Republicans and Democrats who drafted a Senate immigration bill.
Kirk, meanwhile, has been vocal about his belief that the way for Republicans to win more often in Illinois is by being fiscally conservative but socially moderate -- even if they anger the far right wing of the party. Earlier this year, he became the second Republican senator to endorse gay marriage.
"He's broadening his base," Serafin said.
All the palling around is likely to get trickier, though, as their re-election bids approach. Both men will be expected to campaign for each other's opponents and help get each other defeated. With control of the Senate in the balance in 2014, the races could get nasty.
A Durbin spokeswoman said it was too early to talk about 2016. Kirk's office, meanwhile, said only that he will support his party's nominee.
John Tillman, a conservative activist from Illinois, said Kirk should have no illusions that Durbin is against him.
"I hope that's informing (Kirk's) decisions," Tillman said.
Both Durbin and Kirk say their bipartisan relationship has benefited Illinois, especially on projects like speeding up improvements to aging locks and dams on the Mississippi and Illinois Rivers.
Kirk was 52 when he suffered his stroke while traveling to an event in Chicago. He was in intensive care and had a portion of his skull temporarily removed to reduce swelling. Movement on his left side was severely limited.
Within days Durbin and his chief of staff went to Kirk's office, where they gathered his staff and offered to help with anything they needed.
"It was a great pep talk," said Andria Winters, who was then Kirk's deputy legislative director.
It took months of rehabilitation, but Kirk returned to Washington in January. He said he's more conscious now that one's time to accomplish things in Washington is limited.
"For me," he said, "there's so much to do."