There has been a lot of chatter since Barack Obama effectively won the Democratic nomination on June 3 about an Obama (or unity) bounce in the polls. I was--and still am--skeptical about the bounce based on semantics. As I've argued, a bounce--like those after a convention--implies that there is a sudden uptick in polling following a certain event that will eventually regress to the mean (the one established prior to the event occurring). However, has there been a bounce or just an increase in the margin between McCain and Obama that reflects the conditions on the ground (unpopular president and war, poor economy, etc.)? Let's look at that question with the data we now have from June.
The map above shows how much FHQ's weighted averages have changed as a result of the polls that emerged during June. Those states in green show varying degrees of movement toward Obama while the yellow states reflect a shift toward McCain (White states are states where no polls were conducted in June. There was no case where there were new polls, but no change in the average.). From the outset, it is apparent that this map is largely green. There were 37 states where polling was done in June and of those, 31 shifted in Obama's direction. The states that moved toward Obama the most, as a result of the Illinois senator securing the Democratic nomination, are, for the most part, the states where he trailed by the largest margins prior to that point. We see big jumps in the Appalachian states where Obama lost primaries to Hillary Clinton: West Virginia, Kentucky and Tennessee. That grouping of states stretches to encompass Arkansas and Oklahoma as well. Beyond that, there are a handful of typically blue states in that have shown significant shifts toward Obama (A significant shift is defined as anything greater than a two percentage point jump in the weighted average during June. 2 points! Yeah, keep in mind that we are talking about changes in the average here. In other words, some states are more prone than others to significant shifts. On the one hand, large outliers--at least by comparison to the pre-existent data--will pull the average in their direction. But states that have had comparatively little polling are much more vulnerable to bigger shifts.): Massachusetts, Washington and Maine.
And what of McCain? Well, it isn't all bad for the Arizona senator. The momentum is against him, but he is making gains. And the places where he has made gains during the month are swing states: Nevada, Colorado, Missouri and--depending on who you talk to--Oregon and Iowa.
With the exception of Missouri, those are all Obama states in the current electoral college breakdown and comprise 28 electoral votes. That would be enough to pull McCain within 2 electoral votes of victory, but would still put him behind Obama. While Oregon and Iowa may be moving in his direction, some of the other states would potentially be easier pick ups for McCain (Think light blue states on the electoral college map.). States that are both light blue on the electoral college map and light green on the map above (So, Obama toss ups and slight Obama gains during June) are probably more likely targets for McCain than Iowa and Oregon. New Mexico and Pennsylvania fit that bill.
Of the states in white, there are only a couple that seem like they could be competitive in the fall, yet did not have any polls conducted in June. Connecticut and Montana are both leans toward Obama and McCain, respectively, but have shown signs of being in play. They are both less intensely red or blue than they have been during recent cycles. And both are cases where more polling will help to clear the picture. Also, because each has had only a few polls during all of campaign '08 (primary season, too), both are more likely than others to move significantly in one direction or the other.
Was June a bounce month for Obama, though? There's definitely an uptick in the poll numbers since he wrapped up the Democratic nomination, but as of now, there hasn't been any detectable reversion to the pre-June mean.
The Electoral College Map (6/29/08)
The National Popular Vote Plan...and Other Ways of Reforming the Electoral College
The Electoral College Map (6/25/08)