WASHINGTON - Speculation is mounting that US Vice President Joe Biden could make another bid for president.

Biden has not yet announced whether he will join the race for the Democratic Party’s presidential nomination, but reports over the weekend that the 72-year-old former Delaware senator was seriously exploring a bid reignited discussion among Hillary Clinton’s advisers about what his potential candidacy would mean for the contest ahead. Mrs. Clinton has already announced her candidacy for the top post.

The scenario of a Clinton-Biden matchup for Democratic Party's nomination brought mixed emotions inside Mrs. Clinton’s Brooklyn campaign headquarters, according to a report in The New York Times. Many of Mrs. Clinton’s senior staff members previously worked for Biden and hold him in the highest regard, especially after his son, Beau Biden, died in May at the age of 46 after a long battle with brain cancer.

On the other side, billionaire businessman Donald Trump continues to lead the polls in his drive for the Republican Party presidential nomination.

Meanwhile, CBS News confirmed Josh Alcorn, a top political aide to Beau, Biden's late son, joined the Draft Biden campaign that is pushing the vice president to run for president in 2016. In addition to serving as Beau Biden's chief adviser on political and fundraising issues, Alcorn had helped raise money for Biden's 2008 presidential bid. “I’m thrilled that Josh is joining Draft Biden. Biden supporters across the country know how close he was to Beau and his family,” Will Pierce, Executive Director of Draft Biden 2016, said in a statement Sunday.

“Josh joining the Draft Biden effort only increases the seriousness nature of what to date has been an enormously successful effort,” Pierce added.

Biden has always left the door open for a run, but hasn't made any overt steps toward a bid, either. Political observer say Hillary Clinton's e-mail troubles and soft poll numbers in some areas have reignited questions about a backup.

The latest round of speculation about a Biden try was sparked by a column in the Times. Columnist Maureen Dowd wrote that Biden had been "talking to friends, family and donors about jumping in" to the race.

Dowd also wrote that, before he died, Beau "tried to make his father promise to run, arguing that the White House should not revert to the Clintons and that the country would be better off with Biden values."

"My sense is that he's getting closer to making a decision and I'm hoping that decision is he will throw his hat into the ring," said Dick Harpootlian, a longtime friend of Biden's and the former chair of the Democratic Party in South Carolina.

"Democrats have not connected with Hillary Clinton or (Vermont Senator) Bernie Sanders and they're open to another candidate and they're willing to listen. So i don't think it's too late," Harpootlian added.

Biden would arguably be the most experienced candidate on either side: seven years as vice president brokering key deals with the Senate, where he served for 36 years representing Delaware. But his past two bids for the presidency were rocky ones.

The first time, in 1988, he dropped out after news reports revealed he plagiarized part of a speech and inflated his academic record.

In 2008, he got just one percent of the vote in Iowa. Clinton got more than 29 percent. Polls now show she is vulnerable on questions of trust and honesty. But she still leads Biden in a hypothetical matchup, 55 to 13 percent.

In a statement this weekend, the vice president's spokesperson would only say, "As the Biden family continues to go through this difficult time, the vice president is focused on his family and immersed in his work."