In tone and tenor, the Democrat's second round of presidential debates were a step ahead of round one. Here is a distillation of what transpired:

1. Bernie Sanders is back. The democratic socialist senator from Vermont who is again running for the White House as a Democrat was focused and passionate. Unlike his first debate performance, there was no empty rhetoric. Instead, Sanders was unapologetically radical, particularly when defending his Medicare for All single payer health care plan, and forcefully cast himself as the candidate most capable of beating Donald Trump in a general election. Speculation that his time has passed may have been premature.

2. Elizabeth Warren has grown into her major-contender status and is extremely comfortable with it. Case in point: Her decision to actually scold the audience for chuckling as she tried to relate the story of a man struggling to pay the bills as he fights ALS. It's hard not to wonder if Sanders' resurgence has been spurred, in part, by a recognition that he needs to up his game to keep pace with Warren.

3. For most of the debate, it was Sanders and Warren against everyone else. The duo teamed up to defend their proposals in areas like education and healthcare from criticisms by the moderates on the stage, who repeatedly tried to cast them as unrealistic and radical — a sign that the 2020 campaign could exacerbate the ideological divide inside the Democratic Party rather than resolve it. As for Sanders and Warren, it certainly seemed like they'd agreed beforehand not to go after each other; how else to explain Warren's odd non-answer when asked if her decision to embrace the "capitalist" label was an attempt to differentiate herself from her Senate colleague? At some point, though, whatever detente currently exists seems destined to break down, since each one represents the other's greatest obstacle to the nomination.

4. Immigration is without a doubt a vexing subject. But the only candidate who seemed to understand how potentially explosive it will be in a final election was debate newcomer Steve Bullock, the governor of Montana — a blood-red state that voted overwhelmingly for President Trump, but where Bullock managed to be reelected as the state's chief executive. At one point, Bullock warned that decriminalizing illegal border crossings and offering healthcare to undocumented immigrants will make the current crisis at the border significantly worse. While that argument might not move Democratic primary voters, the candidates might want to ponder it as they prepare to court the independents who could help them unseat President Trump.

5. As admirable as this series of debates may be, the nation will not be able to truly judge the comparative merits of the candidates until the stage holds Sanders, Warren, Karmala Harris, and Joe Biden. Perhaps mayor Pete Buttigieg will get the leg up he needs. Maybe Senators Cory Booker and Amy Klobuchar will finally find their footing. But this field of 20 plus candidates is slowly and surely narrowing.