[NCC-1701]

Not being I them ow about such matters, I have been wondering how it’s known that candidate A is leading candidate B before the votes are counted on Election Day. Any help enlightening me is thanked in advance.

[pgkdan]

They're making assumptions based on whose voting, the party registration of those requesting early or absentee ballots and where these votes are coming from. If a counnty in OH that went for McCain in 2008 is having a strong early voting turnout it's assumed that a majority of those early votes will be for Romney.

Gallup and Pew are getting their numbers from their polling. They're compiling stats on who's already voted and who they say they're voting for.