Source: CBS documentary
By 1968, television became the most important source of news for the American public, and, possibly, the most powerful influence on public opinion itself. TV brought the war from the frontlines and jungles of Vietnam into the living rooms of the American people. The intensely negative coverage of the war such bombings, brutality and civil casualties by US military influenced both politicians and the American public. This resulted in growing outrage and anti-war movement, which strongly affected 1968 presidential elections. American public lost trust in current administration, while new coming candidates were able to use this hot issue for their advantage.

Vietnam War with Walter Cronkite, CBS documentary
1968
http://www.youtube.com/watch?v=S3mfXnFtwQc
http://www.youtube.com/watch?v=IPmwkprZMic&feature=relmfu

Source: Brown University
In this interview Governor Lincoln Almond tells us that by 1968 Vietnam war became very divisive for the nation and he personally was taking part in many anti-war demonstrations. The war was taking its toll on Lyndon Johnson and, as a result, he was forced to withdraw from 1968 presidential race and give up his chances for his second term in the presidential office.

Interview with Governor Lincoln Almond
Spring, 1998
http://www.stg.brown.edu/projects/1968/narrators/L.ALMOND.html

Source: AP Images database
This picture illustrates the police brutality against peace movement demonstrators in Chicago just few months before presidential election of 1968. This shows inhumane methods politicians used to suppress anti-war movement, which was unpopular topic during the political campaign. Picture speaks a thousand words!

Original caption: 8/28/1968-The “Black” Year (Tenth of Fourteen) – Police and demonstrators are in a melee near the Conrad Hilton Hotel on Chicago’s Michigan Avenue August 28th during the Democratic National Convention.
Copyright Bettmann/Corbis / AP Images
http://www.apimages.com/police_demonstrators_Chicago_August_28th_DNC