"If you really want a winning ticket, this is it," Sen. Diane Feinstein, D-Calif., said in a June interview on "This Week with George Stephanopoulos". "I've looked at every other possible candidate. No one brings to a ticket what Hillary brings -- 18 million people committed to where she's going."
Feinstein and other Clinton allies argued the wide support she received during the primaries from white, blue-collar workers, women, Hispanics and older voters would boost Obama's chances in key battleground states.
"I think she has the qualifications to be president, and I think she would be very strong as a campaigner. So you're doing the two things that need to be done to be qualified," New Jersey Gov. Jon Corzine, a Democrat, said July 30 on MSNBC's "Morning Joe."
Other Clinton supporters had publicly suggested the former first lady would have been the nominee had news of former Sen. John Edwards' affair with Rielle Hunter broke during the Democratic primaries.
"I believe we would have won Iowa, and Clinton today would therefore have been the nominee," former Clinton communications director Howard Wolfson told ABCNews.com.
"Our voters and Edwards' voters were the same people," Wolfson said the Clinton polls showed. "They were older, pro-union. Not all, but maybe two-thirds of them would have been for us and we would have barely beaten Obama."
A small minority of Clinton supporters are even refusing to vote for Obama, arguing Clinton won the Democratic primary's popular vote if Michigan and Florida votes were fully counted -- though Obama's name wasn't on the Michigan ballot and both primaries were held early against the will of the national Democratic Party.
"I really don't care who he chooses as vice president because I'm not going to vote for him regardless," Democrat Will Bower recently told ABCNews.com.
Bower is the co-founder of PUMA, which stands for Party Unity My A**, a Washington-based group urging Clinton to fight for the nomination all the way to the party's convention next week in Denver.
But other former Clinton backers argued the former first lady would have outshone Obama -- a no-no for any running mate or vice president.
"She is such a towering personality that she could have occupied a great deal of media real estate on her own, complicating Obama's challenge of communicating who he is directly to the public," said Chris Lehane, a Democratic strategist and former Vice President Al Gore's presidential campaign spokesperson in 2000.
Political analysts argue Obama needed to pick someone he could trust and get along with for the next four to eight years, should he win the White House.
Obama's relationship with Clinton was put under further scrutiny this month when leaked emails from Hillaryland revealed just how far some Clinton supporters were willing to go to push Obama out of the primaries.
In a strategy e-mail to Clinton and her top advisers, former Clinton strategist Mark Penn's wrote, "I cannot imagine America electing a president during a time of war who is not at his center fundamentally American in his thinking and in his values.
"Let's explicitly own 'American' in our programs, the speeches, and the values. He doesn't," Penn added. "His roots to basic American values and culture are at best limited."
Clinton did not heed Penn's advice.
There is also the matter of whether Clinton truly wanted the job.