Numbers available Tuesday show Democrats outnumber Republicans by less than 1.1 million voters. That compares to the 1.2 million voter advantage Democrats held when President Barack Obama won Pennsylvania in 2008.
Political scientist Christopher Borick of Muhlenberg College in Allentown says odds are that fewer voters will be registered in this election, compared to 2008.
The current total of about 8.3 million voters is less than in the 2004 presidential election.
This year, Democrats are doing better at signing up new voters, while Republicans are getting more to switch.
Oct. 9 is the deadline to register.