And it won't be the last time either. Well it might actually depending on how the primary ends.
I searched of Romney vs Obama (RCP average,2012)
Romney was ahead 3 times in
October,9th,2012 (Romney 48.0 Obama 47.3)
October,19th,2012 (Romney 47.1 Obama 47.0)
November,1st,2012 (Romney 47.4 Obama 47.3)
Tied 4times
September,3rd Romney 46.3 Obama 46.3
September,5th Romney 46.8 Obama 46.8
September,5th Romney 46.7 Obama 46.7
October,31th Romney 47.4 Obama 47.4
http://www.realclearpolitics.com/epolls/2012/president/us/general_election_romney_vs_obama-1171.html#polls