JF,
It is all in the numbers, Springfield's voters combining with West, North, and the portions of South and for a lack of a better term Coburg Road area voters is a sizable voting block, especially if the cost savings and benefits of a merger are promoted to that constituency.  While I grew up near Alvadore, I attended Bethel schools and I know Springfield intimately once owning a home in the Thurston area.  The difference between the two is minimal for the vast majority of the two cities populations.  The real difference seems to be the so called "elite" of Eugene.  Reduce their power (merge and county seat) and real, sustainable, positive change can occur.  Otherwise the folks living there (especially Eugene) will continue to repeat the same ol, same ol and go nowhere with the pie continuing to get smaller and smaller.