Is Russia really behind the DNC email hack?

Russians behind DNC hack?

The stated theme for night one of the Democratic National Convention is "United Together." But the reality is deep divisions.

Late Monday, the Democratic National Committee apologized to Bernie Sanders for leaked e-mails which, among other things, questioned his religious beliefs. The controversy forced the outgoing DNC chair to give up her duties at the convention, including gaveling it to order.

The Hillary Clinton campaign is blaming the email leaks on Russia, reports CBS News' Julianna Goldman.

For a second day, Clinton's campaign manager Robbie Mook accused Russian President Vladimir Putin of meddling in the U.S. election.

"What the experts said when this breach initially happened at the DNC was that they believed that it was Russian state actors who took these emails," Mook said. "Russian state actors were feeding the emails to hackers for the purpose of helping Donald Trump."

The experts he's citing include an outside group hired by the DNC to investigate the cyber intrusion, which in June said it identified "advanced methods consistent with nation-state level capabilities."

But neither the Clinton campaign, the White House, nor lawmakers briefed on the hack definitively linked the leak to the Russian government on Monday.

What we know about the DNC email hack

Donald Trump's campaign chairman Paul Manafort called the accusations absurd.

"It's pure obfuscation. of the Clinton campaign. What they don't want to talk about what is in the e-mails."

For Clinton's team, a Putin-Trump bromance is an easy diversion from the emails, which re-opened a rift in the Democratic party as it tries to present a united front in Philadelphia.

"In terms of leadership, [Putin]'s getting an A," Trump said in a past interview. Putin has also praised Trump and a number of Trump's advisers have ties to the Kremlin.

Manafort advised pro-Russian, Ukrainian oligarchs including former President Victor Yanukovych -- a Putin ally who fled to Russia in 2014 after corruption accusations.

The FBI announced Monday it is investigating the hack, and promised to hold accountable those who pose a threat in cyberspace.