The second session of this week's CNN Democratic debates in Detroit quickly morphed Wednesday night into an all-out attack on Democratic Party front runner Joe Biden, with Kamala Harris, Cory Booker, Kirsten Gillibrand and others blasting the former Vice President on a variety of issues, as several Democrats criticized Biden over certain policies of the Obama Administration.

"I have guts enough to say his plan doesn't make sense," Biden said at one point, knocking away the criticism of Julian Castro, who denounced large scale deportations of illegal immigrants by President Obama, comparing it to the policies of the Trump Administration.

"To compare him to Donald Trump, I think is absolutely bizarre," Biden countered, as he repeatedly counter punched against his Democratic challengers.

Here's a rundown of what we learned from the second Democratic debate.

1. Biden swarmed in second debate. After a somewhat uneven first debate last month in Miami, former Vice President Joe Biden was more aggressive in pushing back more against his Democratic Party critics on Wednesday night - but the attacks kept coming from almost every angle on stage. Harris ripping him on opposition to Medicare For All. Booker blasting Biden over the 1994 crime bill. Gillibrand digging up an old op-ed about working women. DeBlasio questioning Biden on his trade views. Castro knifing him on immigration. Inslee demanding more on climate change. Biden did not have a perfect night by any means.  But the direction of the attacks certainly made clear who the front runner was in this debate.

2. More evidence of health care divisions. For a second straight night, Democrats in this CNN debate got into a deep policy dive on the question of health care, and whether the feds should embrace the idea of "Medicare For All," which could mean the end of private health insurance policies. "The Senator has had several plans so far," Biden said, jabbing at Kamala Harris over her new Medicare For All health plan, which Biden said would cost too much money and not work for consumers. "It's a bunch of malarkey," he said at one point. Michael Bennet also denounced the idea, while Bill de Blasio implored Democrats to quit making excuses, and go big on health care.

3. Democrats attack Biden over Obama policies. A lot of things have gone sideways in politics over the last few years, and that was very evident during the second debate - as a number of Democrats ripped Biden over policies of President Barack Obama. You read that right. First it was on immigration - where more progressive Democrats now recoil at Obama's efforts to deport illegal immigrants. In a broadside leveled directly at Biden, Julian Castro - who served in the Obama Cabinet - said Biden should have objected to deportations. "One of us has learned the lessons of the past and one of us hasn't," Castro said bluntly. To some Democrats, the scene was beyond belief. "It's just odd to me that the Obama record seemed to get attacked more tonight than the Trump record," said Rep. Brendan Boyle (D-PA), as a former top Obama aide cautioned Democrats to think twice.

4. Whither the Democratic long shots? One of the big questions this week in Detroit was whether or not some of the long shot candidates - many of whom have been mired at 1 percent or lower in the polls - could find a magic debate moment to jump start their campaigns. They certainly tried - but it wasn't clear that there was going to be a massive shakeup. Tuesday night brought online interest in Marianne Williamson, who top Democrats probably wish would just disappear. Wednesday night brought strong lines by Booker and Castro, but maybe not others. "I'm Jay Inslee and I'm running for President," the Governor of Washington said at one point - drawing derisive comments immediately on Twitter.

5. The next debate could be the real deal. If the rules for the Democratic debate in mid-September stay the same, there could be as few as seven or eight candidates on stage, and that would guarantee the first direct debate clash between Joe Biden and Elizabeth Warren. And for many, that's the debate which is needed to sort out the direction of the 2020 race for Democrats.   In a sense, Warren v Biden would almost become the 2020 version of Sanders v Clinton, with Warren representing the progressive effort to topple the Democratic Party status quo.