DENVER – Again, the Clintons proved why they are the most adept political couple in America today.

Did anyone really doubt that Sen. Hillary Rodham Clinton and former President Bill Clinton would deliver a seal of approval of Democratic nominee Barack Obama?

The doubters hadn’t studied the Clintons.

Bill Clinton’s blessing, especially, was direct and personal.

“Everything I learned in my eight years as president – and in the work I’ve done since in America and across the globe – has convinced me that Barack Obama is the man for the job,” he told a raucous Pepsi Center crowd.

Clinton, who at times during the long campaign seemed resentful of Obama’s success, actually gave a more robust, and potentially more significant, endorsement than Hillary. While she spent a lot of her prime-time speech Tuesday recounting the successes of her campaign and sending a not-so-subtle “keep going” refrain to her supporters, the former president made a more direct case for Obama.

Former President Jimmy Carter noted the distinction in an interview with USA Today and Gannett News Service. But for the most part, Carter said, the Clintons had performed “superbly” under “difficult political and emotional” circumstances.

If Obama loses this election, many will ask why he devoted two nights of his convention to the Clintons. The long goodbyes were a testament to both the emotional appeal of Hillary Clinton for many Democrats and the fierce attention both Clintons pay to their legacy and viability.

Had they or their supporters disrupted the convention and not gone all in for Obama, another Hillary path to the White House would have been demolished.

Maintaining political viability has been a lifelong pursuit for Bill Clinton. When he first ran for president in 1992, a letter surfaced that a 22-year-old Clinton wrote in 1969 to the head of the ROTC program at the University of Arkansas. The letter became central in a fierce debate about how Clinton was able to avoid the draft during the Vietnam War.

Despite being against the Vietnam War, Clinton wrote Col. Eugene Holmes that he decided to enter the draft “in spite of my beliefs for one reason: to maintain my political viability within the system. For years I have worked to prepare myself for a political life characterized by both practical political ability and concern for rapid social progress.”

Is the Clinton era over forever? That depends on what happens Nov. 4. Should Obama lose, Sen. Clinton would immediately become her party’s favorite for 2012. But should Obama win, some of her colleagues in the Senate believe that is where she will leave her mark.

“She is an extraordinary person, a great senator from New York,” said Sen. Dick Durbin, D-Ill. “She can become an extremely important person in the United States Senate, if that is her choice.”

Peter Groff, a Democratic state senator and Obama’s Colorado campaign co-chairman, said he believes Sen. Clinton will become a “lioness” in the Democratic Party much the same way that Sen. Edward Kennedy, D-Mass., is often described as a “lion” of the Senate.

Meanwhile, Obama needs the Clintons’ help. Obama’s top campaign strategists David Plouffe and David Axlerod told reporters Thursday they expected both Clintons to campaign on Obama’s behalf this fall. How much remains to be seen, but Durbin thinks Sen. Clinton will be deployed to the rural and small-town areas of the Rust Belt where she tromped Obama in the Democratic primaries.