Maybe this is just a coincidence: Sen. Joseph Biden (D-Del.) devoting a lot of his time to attacking Sen. John McCain (Ariz.), the GOP presidential candidate, on foreign policy and national security.

Biden has been out of the presidential campaign for months. Yet his role as a self-proclaimed surrogate for Sen. Barack Obama (Ill.) — the Democratic standard-bearer who is weak where Biden is strong — has some wondering if he’s looking for a spot on the ticket.

“I’d make a great president. I’d make a great secretary of state. I’d make a great vice president,” Biden joked this week.

Yet Biden has had few laughs when attacking McCain, calling him “out of touch” with the needs of the troops and accusing the GOP candidate of considering himself “above the law” on national security.

Biden’s ability to throw sharp elbows could be what Obama needs in a running mate: a tough and experienced veteran to neutralize McCain’s military and national-security credentials, the centerpiece of the Republican candidate’s campaign.

If asked, Biden says he would not turn the job down. But he says he’s not auditioning, as some speculate.

“They don’t know me, and I don’t give a damn,” Biden said.

“My role is self-appointed” in the Obama campaign, Biden said. “As a Democrat, I am not sitting still for any Republican suggestion that the Democratic position on national security is weak. The Republicans have been an absolute total disaster, by their own measure.”

Biden said he is modeling his new efforts on an approach he employed in the 1980s and 1990s, when Democrats effectively rebutted Republican criticism that they were soft on crime after they pushed through major anti-crime legislation.

Elected to the Senate at the age of 30, the 65-year-old Biden has a laundry list of foreign and domestic policy achievements and harbors deep ambition to occupy the Oval Office. A Catholic born in the swing state of Pennsylvania, Biden could also appeal to working-class whites, a constituency Obama had a hard time courting in the primaries.

The senator, who dropped his own bid for the presidency after a poor showing in January’s Iowa caucuses, was praised for his solid performances and wit at Democratic presidential debates last year.

“Joe brings an extraordinary knowledge of the world and of the world’s leaders that few Democrats or Republicans in the Senate or outside the Senate possess,” said Democrat Tom Carper, the junior senator from Delaware. “Sen. Obama … does not have the depth of experience in foreign policy that Joe Biden’s 30-plus years has.”