At times it seems like President Barack Obama and Governor Mitt Romney are campaigning for the presidency of only one state -- Ohio. Always a pivotal battleground, thanks in part to its 18 electoral votes, this diverse state in many ways mirrors the country and is once again poised to decide the election. Not only has no Republican been elected president without winning Ohio, the state has also picked the White House winner in the past 12 elections. It's a must-win for Romney, but also integral to several paths the president has to reaching the magic 270. Here's a look at how crucial Ohio is to the presidential contenders -- and the regions and voting blocs vital to winning the state.Left: Shadows of Mitt Romney and Paul Ryan supporters are cast on a wall displaying the Ohio state flag during a campaign event at Baldwin Wallace University in Berea, Ohio, on Oct. 17, 2012.