Unsurprisingly, one of the first questions ABC moderators asked at the Democratic debate was about the controversy that's consumed the campaign for the last 48 hours: the allegations that Bernie Sanders campaign staffers improperly accessed data from the Clinton campaign on a voter database, and the DNC's decision to lock the Sanders campaign out of the database entirely in response.
In what probably wasn't the hardest-hitting follow-up question a moderator has ever asked in 2015, ABC's Martha Raddatz asked Sanders directly, "Does secretary Clinton deserve an apology tonight?"
"Yes. I apologize," Sanders replied.
Sanders' explanation of what went down is pretty clear, if you understand a couple of the terms he uses. By "vendor" he means the company NGP VAN, which runs the voter database used by Democratic campaigns (including the Sanders and Clinton campaigns). The NGP VAN database allows all candidates to access basic voter records, but allows individual campaigns to put in their own data for private use. That's the data that was "breached" by the Sanders campaign.
When Raddatz asked Clinton if she accepted the apology, Clinton was clearly ready. During the first Democratic debate, Sanders was generally understood to have done Clinton a favor by declaring, "The American public is sick and tired of hearing about your damn emails"; Clinton returned the favor during the ABC debate, saying, "I don't think the American people are all that interested in this. I think they're more interested in what we have to say about all the big issues facing us."