According to Political Wire (originally sourced from Newsweek), the Obama campaign sees five paths to 270 electoral votes, all starting with the assumption that Obama will win all the states captured by John Kerry in 2004.

Those states awarded 252 electoral votes (although Kerry only received 251 electoral votes as a Minnesota elector voted for John Edwards). As a result of the 2010 Census, those same states now award 246 electoral votes.

Here are interactive versions of the 5 strategies. Which strategy is most likely to be successful? What if the basic premise (of winning all the Kerry states) is wrong? These maps are editable.... use them as a starting point to test the Obama campaign's beliefs against your own. 

1. West Path: 2004 Kerry states +  Colorado, Iowa, Nevada and New Mexico  (the Newsweek article leaves Iowa out)
2. Florida Path: 2004 Kerry states + Florida
3. South Path: 2004 Kerry states + North Carolina and Virginia
4. Midwest Path: 2004 Kerry states + Iowa and Ohio
5. Expansion Path:  2004 Kerry states with a loss in Pennsylvania and New Hampshire, offset with gains in Arizona, Colorado, Iowa, Nevada, New Mexico and Virginia.   (this strategy is not fully spelled out in the article).