Outside of the segment on Trump's indictments and his behavior on Jan. 6, it's been a bit surprising that there's been little discussion of him otherwise. There've been a few references to actions taken prior to Biden taking office, indirectly involving Trump, but not much specifically about him. That has turned this debate into something of an alternative universe where these are the main eight candidates, not the eight who are badly trailing the main guy not in the room.
-Analysis by Geoffrey Skelley of FiveThirtyEight

Yeah, Maya, I am surprised Trump didn’t come up more. With him not on stage, I actually thought it would be easier for the candidates to swipe at him, since there was no risk of him punching directly back. But with some notable exceptions, like Christie and Hutchinson (and even then, only on a couple occasions), the candidates showed little interest in hammering away at the primary front-runner. I think that’s a questionable strategy since none of these candidates will be able to earn majority support in the primary without stealing some of it from Trump.
-Analysis by Nathaniel Rakich of FiveThirtyEight

Sixty-eight percent of Americans think the government is withholding information about UFOs, and three-fourths think there is some form of life on other planets. The number of Americans who suspect UFOs have been spotted has also increased, and 41 percent believe that some spotted UFOs are alien spacecraft. This has only been increased in recent years with Navy pilots reporting strange sightings over the past decade, along with recent congressional hearings about the issue.
-Analysis by Monica Potts of FiveThirtyEight

Christie was seen smiling and shaking his head as Fox News moderator Martha MacCallum began to ask about UFO ecounters.

"I get the UFO question? Come on, man!" Christie said.

"I think it's horrible that just because I'm from New Jersey, you asked me about unidentified flying objects and martians," he continued. "We're different but we're not that different."

Recent election cycles have shown how debates can substantially alter a candidate’s trajectory. The debates won’t always do this, of course, and early primary polls remain relatively predictive of who will end up winning a party’s nomination. However, a candidate can earn a real polling bounce from a debate — or fall into a valley.

Primary polls are inherently more volatile than general election polls. In a general election, most voters already lean toward one party, so only a small part of the electorate is likely to shift its views over the course of a campaign. But in a primary, voters in one party may be open to multiple candidates because most contenders will share similar views on a number of issues. As a result, exposure to an unfamiliar candidate could prompt voters to begin considering that contender, while a strong or weak performance by a candidate they do know could make them look elsewhere.

For example, early in the 2012 cycle, Texas Gov. Rick Perry appeared to be now-Sen. Mitt Romney’s most serious opponent for the Republican nomination. But in a September 2011 debate, Perry defended a Texas policy that gave undocumented immigrants access to in-state college tuition. The backlash from the GOP base came swiftly, as Perry fell out of contention in the polls, well before a later debate in which he — oops — forgot the name of the third of three federal agencies that he aimed to dismantle as president. Four years later, former tech executive Carly Fiorina had very little support early in the 2016 Republican race, but in August 2015 she stood out in an “undercard” debate. Her polling numbers improved and she made the main stage in subsequent debates, giving her a platform that eventually led Texas Sen. Ted Cruz to make her his vice presidential pick in a last-ditch attempt to rally support against Trump in the 2016 primary.

-Analysis by Geoffrey Skelley of FiveThirtyEight