With less than six months until 150m US voters head to the polls, the likely candidates in the 2012 presidential election are already eyeing the so-called "swing states" necessary to secure victory.

As far back as 1888, these battleground states where no single candidate or party can secure overwhelming support, have played key roles in determining an election's outcome.

This year, incumbent Barack Obama, and Mitt Romney, the presumed Repubican candidate, will look to states like Pennsylvania to move one step closer to the 270 electoral college votes needed to win the presidency in November.

Al Jazeera's Scott Heidler reports from one of those swing states, Pennsylvania.