Democrats are worried that the furor surrounding Hillary Clinton's private email server will be prolonged and intensified after her sudden move to hand it over to the FBI.

The Clinton campaign's decision to give up the server and a thumb drive containing backup copies of emails left Democrats scratching their heads as to why the former secretary of State had resisted for months turning over the server.

Coupled with new polls that suggest Clinton is vulnerable, Democrats are nearing full-on panic mode.

"I'm not sure they completely understand the credibility they are losing, by the second," said one Democratic strategist, who spoke on the condition of anonymity. "At some point this goes from being something you can rationalize away to something that becomes political cancer. And we are getting pretty close to the cancer stage, because this is starting to get ridiculous."

Vice President Joe Biden is using part of his vacation in South Carolina this week to sound out friends and family about a presidential bid, as some Democrats press him to enter the race and give the party another option in the face of lingering controversies involving Hillary Clinton.

From his vacation spot on Kiawah Island, Mr. Biden is giving the strongest signal yet that he is actively considering making a third run at the presidency. He is asking political allies for advice and gauging the strength of Mrs. Clinton's campaign as he weighs his options, people familiar with the matter said. Mr. Biden is expected to announce his decision next month.

"He's taking input from a lot of people he cares about and respects," said James Smith, a South Carolina legislator and Biden supporter who said he has urged the vice president to run. "He knows where I stand. It's just got to be his decision."

Warren bowed out of this race months ago in deference to Hillary. But now that Hillary is mortally wounded, I can already see the "heroic" press conference. I could write the script.

Elizabeth Warren will step up to the podium and say, "I've been a fighter for underdogs my entire life. I've fought for women, African Americans, Hispanics, gays, unions, the poor, the working class, mothers on welfare, children without enough food to eat. In light of Hillary Clinton's distractions, I have decided for the good of this country and my party to re-think my decision. I believe my party needs me. I believe my country needs me. Consumers need me. The working class needs me. So…I've decided to enter the race for president of the United States."

And just like that … Hillary is done.