Mitt Romney's campaign has bought air time in Pennsylvania, saying in a memo that the Democratic-leaning state now represents an opportunity for the Republican campaign.

"Pennsylvania presents a unique opportunity for the Romney campaign," political director Rich Beeson wrote. "Mitt Romney is more competitive in the voter-rich Philadelphia suburbs than any Republican nominee since 1988." 

President Obama's campaign cast the move as desperation rather than momentum.

"[T]he Romney campaign has found itself with a tremendously narrow and improbable path to 270 electoral votes," Obama campaign manager Jim Messina said in a statement. “Now, like Republicans did in 2008, they are throwing money at states where they never built an organization and have been losing for two years."

Obama's lead in Pennsylvania is narrow but consistent; Romney hasn't led a poll in the state since February. 

Romney's campaign did not disclose the size of ad buys, but according to NBC News the buy so far is at least $120,000. Restore Our Future, a pro-Romney super PAC, recently placed a $2.1 million buy in Pennsylvania. 

Obama has spent about $5 million in Pennsylvania, mostly over the summer. The campaign is countering the Restore Our Future ads with a buy of at least $650,000, concentrated in Philadelphia.