Lingering bitterness from the heated primary campaign between Clinton and Sanders erupted after more than 19,000 Democratic National Committee emails, leaked on Friday, confirmed Sanders' frequent charge that the party played favorites in the race.
"What the experts said when this breach initially happened at the DNC was that they believed it was Russian state actors who took these e-mails. And what further experts are saying, and again I refer you to the reporting on this, but further experts are saying is that then, because they possessed those e-mails, that Russian state actors were feeding the e-mail to hackers for the purpose of helping Donald Trump," said Clinton's campaign manager Robby Mook during a news conference in Philadelphia on Monday.
The head of the Democratic Party resigned on Sunday amid a furor over embarrassing leaked emails, hoping to head off a growing rebellion by Bernie Sanders supporters on the eve of the convention to nominate Hillary Clinton for the White House.
The furor was a blow to a party keen on projecting stability in contrast to the volatility of Republican candidate Donald Trump, who was formally nominated at a raucous convention in Cleveland last week.
It also overshadowed preparations in Philadelphia for Clinton's coronation as the nominee to face Trump in the Nov. 8 presidential election. She will be the first woman nominated for president by a major U.S. political party.
The four-day Democratic convention will open on Monday. In some good news for Clinton, The New York Times reported that businessman and former New York City Mayor Michael Bloomberg will endorse her in a prime-time speech on Monday, saying she will be the best choice for moderate voters in 2016.
The cache of emails leaked on Friday by the WikiLeaks website disclosed that DNC officials explored ways to undermine Sanders' insurgent presidential campaign, including raising questions about whether Sanders, who is Jewish, was really an atheist.
The Clinton camp questioned whether Russians may have had a hand in the hack attack on the party's emails and were interested in helping Trump, who has exchanged words of praise with Russian President Vladimir Putin.