Editor's Note: (Julian Zelizer is a professor of history and public affairs at Princeton University, and author, with Kevin Kruse, of the new book "Fault Lines: A History of the United States Since 1974." Follow him on Twitter at @julianzelizer. The opinions expressed in this commentary are his own. View more opinion at CNN.)
(CNN) NBC News has announced the eagerly awaited lineup for the first two televised debates between the Democratic candidates, to be held in Miami later this month.
And there's a reason why the Wednesday and Thursday debate rosters can matter.
Sens. Elizabeth Warren and Bernie Sanders have been separated. Warren is in the Wednesday group, giving the senator from Massachusetts the first -- potentially more high-profile -- shot at being mover and shaper of the policy conversation. She may also set the standard for the progressive alternative to former Vice President Joe Biden, who is in the Thursday group.
Biden has been clustered with a number of his higher-polling competitors, including Sanders, Sen. Kamala Harris and South Bend, Indiana, Mayor Pete Buttigieg, which means that he could come under tougher fire than he might have on the first night.
But even before the announcement, three Democrats were furious that they didn't qualify. Montana Gov. Steve Bullock, Rep. Seth Moulton of Massachusetts and Miramar, Florida, Mayor Wayne Messam failed to garner the required 1% support in three polls or donations from 65,000 people (or both). As The New York Times noted Thursday, parties knocking candidates out of the prime-time spots based on early polling can indeed be a mistake. In 1992, Paul Tsongas wasn't even at 1% in the early polls but was able to defeat Bill Clinton in 15 contests. Had the current debate chess rules been in effect, Jimmy Carter would never have made the screen.
Given these and other factors, it is worth asking: Are these debates really so important? Well, yes. While there is a tendency within the media to exaggerate the long-term impact of any of the events that take place along the way of a presidential campaign -- including these debates -- the candidates (the chosen and the bumped) know the importance of televised faceoffs is real.
To be sure, the nature of party candidate selection has been changing in significant ways. Winning the nomination is no longer primarily about retail politics, for example, nor is it all about the local anymore. The number of national media events and moments that take place before the Iowa caucus and New Hampshire primary is now immense. The permanent campaign is a reality.
What we have witnessed over the past two decades is the construction of a vast media-political complex that covers and analyzes politics on a full-time basis.
It started with cable television in the 1980s and 1990s, which soon became a dominant form of news, filled with stations -- some partisan, some neutral -- devoted to covering politics almost 24 hours a day and 365 days a year. This automatically extended the time of the political campaign by creating vast amounts of airtime where politics would be reported on, discussed, debated and analyzed long before the first caucuses and primaries took place.
The expansion of the internet in the late 1990s and early 2000s only strengthened this new world of media. The internet created an online community with an instantaneous and global reach, breeding online newspapers, magazines, blogs and bulletin boards focused on upcoming campaigns. Politicians were often forced to respond to stories that emerged in this space from the moment their candidacies became clear. Some of them, astute about the opportunities taking shape, tried to exploit this part of the media landscape to build the kind of momentum and excitement that were once reserved for early caucuses and primaries.
Then came social media -- Facebook (2004), YouTube (2005) and Twitter (2006) -- adding yet another dimension to the vast universe of political information. The kinds of editorial and production controls on information that still existed in the formative era of cable disappeared.
Candidates could speak directly to voters whenever they wanted. Voters, commentators, political operatives and anyone else could get their message out right away. Viral moments meant that a candidacy could be made or broken within a few hours outside of any voting.
The impact of all this media space for campaign politics, and the thirst for content, became clear in the 2016 primaries, with a series of televised debates that took place in both parties during 2015 and 2016. Republicans put together a two-tiered structure, given the huge number of candidates who were running. Voters were bombarded with campaign events from both parties. The Republican contest was more like a WWE steel cage match filled with contestants while the Democratic primaries took on the drama of a Frazier-Ali series of boxing matches.
So, there is a good reason that candidates are extremely focused on their placement, the structure and the format.
While none of these debates will likely be a make-or-break moment, in a field this crowded they could have a very significant influence on elevating candidates and helping Biden's opponents gain more traction against him. They will also create opportunities for candidates, including Biden, to stumble.
The power of this media-political complex has already been made clear yet again with the meteoric rise of Buttigieg, who has used interviews and carefully tailored tweets to make a serious candidacy for himself. And in her own way, Warren has figured out how to use the announcement of substance-based policy plans as a way to keep media attention as she gradually climbs in the polls.
Debates are never what they are hyped up to be, but they are extremely significant in this politically cluttered age. Candidates face each other -- unmediated by aides and Twitter -- and American voters, just on the other side of the camera, get a look at who they are. They need to respond to challenges in real time and they are forced to handle the back-and-forth with opponents rather than find shelter in the silo of a campaign.
The cumulative effect of the events starting in June and going through Super Tuesday can set the terms of the actual voting that will take place between Iowa and Super Tuesday.