Early in this campaign we were treated to the Obama camp promising to "expand the field" and campaign hard to win traditionally Red States.www.mydd.com/story/2008/5/1/144541/9616
Even Michael Barone said to "throw out the map" http://www.realclearpolitics.com/articles/2008/03/throw_out_the_maps_in_2008.html thinking we would have an "open field election" (I questioned this at the time, BTW)
The sports analogy would be akin to a spread shotgun formation, where a football team tries to use the whole field to set up one-on-one matchups and provide the running game lateral room for big plays, while enabling receivers to get quickly upfield for deep passes.
Speed, elusiveness, and finesse are essential to executing this offensive philosophy. It's hard for a inexperienced quarterback to succeed in this gameplan, because such a triggerman will tend to get sacked, throw picks, or put the ball on the ground a lot., instead of knowing when to just heave the ball in the stands.

Obama had the chance to go this route by choosing Tim Kaine, Evan Bayh, or Kathleen Sebelius. He didn't.
Instead by picking a running mate from a very "Blue" state it is apparent that Team Obama will be narrowing the field and trying the old "smashmouth" football approach of trying to grind out a messy victory in the mud.

In the power running formation, one tries to overload the point of attack with blockers and outmuscle the defenders on a narrow slice of field. The odds for disaster are lower (fewer interceptions, sacks or fumbles) but it is hard to score often or win big over a credible opponent in this fashion. (One problem the Obama camp has with this plan is their candidate lacks any bonafides on old time Democrat bread-and-butter economic issues)
The best electoral argument for Biden is he may help a bit in PA. But there were better picks to do that,even. Surely Ed Rendell or Bob Casey,Jr. have more vote pulling appeal in PA.http://www.cnn.com/ELECTION/2006/pages/results/states/PA/ But Rendell and Casey lacked foreign policy experience. Evidently trying to fill this hole was more important than going to a better electoral choice. Having been seen a lot on Philly TV and growing up a half century ago in Scranton is thin gruel to help Obama in a state he got hammered in during the primaries, and will almost certainly cost him the presidency were he to lose it in the general election..
Biden offers no help in any 2004 red state that I can identify. Hell, even Dick Gephardt might''ve helped in MO if Obama wanted to appeal to tired old DC career politicians.
No, Biden was an effort to firm up the Democrat base and grind out a win along the traditional Democrat/Republican scrimmage line. Which is what we now have at summer's end http://www.realclearpolitics.com/epolls/maps/obama_vs_mccain/?map=10
Instead of the "we can lose Ohio and still win" meme, the Obama camp has pulled its ads in seven red states it was working hard in all summer. http://www.mcclatchydc.com/homepage/story/50084.html
Florida and Virginia are surprising, although Obama has been unopposed on the TV in FL, dropped over $5M , yet failed to overtake McCain. http://online.wsj.com/article/SB121850408634131921.html I presume he'll be back in those places, but I suspect they have thrown in the towel in the other five. Perhaps the reason Obama made such a boring VP choice is they have made the strategic decision that they simply can't execute the "big play" in red states, having lost ground in many despite massive effort.
No, there has not been a huge surge of Obama Republicans, or evangelicals for Obama. There are just a lot of mostly young and well educated Democrats for Obama. The strategy he is left with is to take the 2004 John Kerry voting pattern and put it on steroids. This will amount to trying to squeeze another 120,000 net votes out of Cuyahoga and Franklin counties,http://www.cnn.com/ELECTION/2004/pages/results/states/OH/P/00/ or gin up turnout in Denver and Boulder http://www.washingtonpost.com/wp-srv/elections/2004/co/prescounties/ and hope another state like NM or NV flips.
This will be exacerbated as certainly some voters in VA and IN will be disappointed that Biden was picked over well liked local officeholders. Obama had recently lost some ground in both states http://www.realclearpolitics.com/epolls/2008/president/in/indiana_mccain_vs_obama-604.html http://www.realclearpolitics.com/epolls/2008/president/va/virginia_mccain_vs_obama-551.html and I suspect Obama will find IN drifting out of reach soon.
Especially if Team Mac puts a few hundred GRP behind this ad in the Richmond and Indianapolis ADI's http://www.everydayrepublican.com/2008/08/23/joe-biden-on-barack-obama/
The Biden pick will relieve McCain of worries that his base electoral votes will be at risk. The freedom of decision now rest with his team, who can now decide whether it is their turn to open up the field with an unconventional choice, or look for a conventional pick who can enhance our vote totals in the traditional battleground states and media markets
I have no gripes with Mitt Romney or Tim Pawlenty taking it to Obama-Biden on the traditional line of scrimmage, but boy am I feelin former champion women's jock Sarah Palin about now.