Psychologists have a political theory they have titled the Spiral of Silence which is a phenomenon where voters tell pollsters that they are likely to vote for one candidate, and yet, on election day, vote for his or her opponent.
The theory became known as the Shy Tory Factor in the UK during the 1990s when Opinion polls put the unpopular Conservatives behind Labour in the 1992 election only for the Tories to trounce Labour by 8%.
The explanation was that a person is less likely to voice an true opinion if he feels that it is in the minority for fear of reprisals from the majority.
In America this is known as the Bradley effect, named after Tom Bradley who ran as the Democratic Party's candidate for Governor of California in 1982 and despite most polls showing Bradley with a significant as they went into the election, he inexplicably lost to his white challenger.
With the US election only days away, the possibility of the phenomenon raising its head is being considered by nervous Obama supporters and with reason when the results of the Democratic Primary elections are scrutinised.
In the New Hampshire, polls predicted a large Obama win over Hillary Clinton however, Clinton defeated Obama by three points.
Also up for consideration is the possibility of the reverse Bradley effect where those who have said that they won't vote for a black candidate then do so when in the privacy of the voting booth.
Obama still seems to be maintaining a healthy lead in the opinion polls i have looked at but if this Spiral of silence effect kicks in, the margin of error is suddenly much larger than anticipated.