With only a few days left before Election Day, the presidential election is coming down to only a few states. Swing states Wisconsin, Iowa, Colorado, Virginia, Ohio, Florida, and New Hampshire will determine the outcome, all of which Barack Obama won in 2008. Of these, only Florida is likely to go for Mitt Romney in 2012.

In Virginia it is neck-and-neck, but traditionally Republican states North Carolina and Indiana, which both went for Obama in 2008, will probably switch back to the GOP in 2012 and Romney faces little probability of losing any state John McCain won in 2008.

However, the most efficient way for Romney to win the presidency is to win Ohio and its eighteen electoral votes. No Republican has won the presidency without at least winning Ohio, a state that has voted with the winner of the election in twelve straight times. The Real Clear Politics (RCP) poll average shows Obama with a slim 2.8% lead.

With this in mind, both men on the GOP ticket have been devoting much of their time in the Buckeye State, but the circumstances of the election have also led Romney and Ryan to make a last-minute push for Pennsylvania, a state where registered Democrats outnumber Republicans 4-3.

Choosing to make a concerted effort in Pennsylvania, a state which has not voted for a Republican since 1988, seems like an unusual strategic move. Romney has never led in the state and the most recent RCP average still has Obama with a four-point lead, which is down, but only a little.

If Romney loses Ohio and its eighteen electoral votes, he needs to compensate for them by winning a state Obama won in 2008 and is likely to win again in 2012. Wisconsin, vice presidential nominee Paul Ryan's home state, has ten electoral votes, but has not voted for a Republican for president since 1984. Colorado and Iowa were Obama victories in 2008 with nine and six electoral votes respectively, but Pennsylvania, with twenty electoral votes by itself and close proximity to Ohio is the state the Republicans have selected as the big state they need to flip to make up for a probable Ohio loss.

Just a short time ago Republicans began believing Pennsylvania might be in play. After incumbent Democratic Senator Bob Casey looked poised for an easy re-election, self-funding Republican challenger Tom Smith hit Casey with a barage of ads tying him to President Obama and came within one point of Casey in a late October Rasmussen poll.

The newest polls reflect a significant Casey lead, except for Rasmussen and Susquehanna which both show a one-point lead for Casey at the moment. However, it may be unsurprising that if Obama was insufficient to derail Casey, he would be equally difficult to defeat in his own right.

The difficulty lies simply in numbers and turnout. According to the Washington Post, the closest a recent Republican has come to winning Pennsylvania was President George W. Bush in 2004: "For Romney to win, Obama would have to do worse than Kerry and Romney would have to do better than Bush."

It will soon be known whether Pennsylvania was a smart investment for Romney and Ryan, but with little time remaining, it is a decision born out of few options.