CBS This Morning recently highlighted some Presidential debates in this segment: Nixon vs. Kennedy (1960), Reagan vs. Carter (1980), Bush vs. Gore (2000) and Bush vs. Kerry (2004). Presidential historian - Douglas Brinkley and hosts Anthony Mason and Rebecca Jarvis - and especially the Video themselves emphasized the importance of the body language.
One video in particular which stands out here is Bush vs. Gore. During a moment when George Bush was answering, Al Gore conspicuously walked closer to Bush - into his personal space. This was probably deliberately performed in an effort to try and intimidate Bush. It backfired. Even Gore supporters felt uncomfortable watching this nonverbal mistake.
Interpersonal space - often thought of as a series of invisible bubbles surrounding us and dictating how close a person may approach - is variable depending on many factors. In a debate scenario (with the exception of the beginning and the end when the handshakes take place) this space is wider than usual - particularly with their chairs being positioned a good distance apart. As Brinkley points out, the look Bush gave Gore after Al approaches evoked empathy for George in most who were watching. The combination of these two nonverbals linked in succession had a powerful impact on the results of this debate. Intriguingly, George W. Bush went on to have a good bit of his own interpersonal faux pas.
Analysis # 2125: Presidential Debate Body Language - George H.W. Bush, Bill Clinton and Ross Perot 1992
Analysis # 346: Rick Perry Forgets: 8 Republican Presidential Hopefuls Debate in Detroit - 60 seconds of Oops, Body Language and Empathy