Figures on percentage support of each candidate by state taken from FiveThirtyEight blog.
Solid Obama (90%+ support) 19 states (incl. DC) 237 Electoral College votes
CA, CT, DC, DE, HI, IL, MA, MD, ME, MI, MN, NJ, NM, NY, OR, PA, RI, VT, WA
Likely Obama (between 75% and 90% support) 2 states 16 Electoral College votes
NV (76%), WI (82%)
Leaning Obama (Less than 75% support) 5 states 50 Electoral College votes
Colorado (52%), IA (67%), NH, (67%), OH (74%), VA (53%)
All Obama Support: 25 states and D.C. 303 Electoral College votes
Solid Romney (90% + support) 23 states 191 Electoral College votes
AL, AK, AR, AZ, GA, , ID, IN, KS, KY, LA, MO, MS, MT,NE, ND, OK, SC, SD, TN, TX, UT, WV, WY
Likely Romney (between 75% and 90% support) 1 state 15 Electoral College votes
Leaning Romney (less than 75% support) 1 state 29 Electoral College Votes
All Romney Support: 25 states 235 Electoral College votes
538 total electoral college votes; 270 electoral College votes needed to win.
Romney needs to win 35 out of the 50 electoral college votes currently supporting Obama by less than 75% in the polls. In order of weakness of Obama lead: CO (52%, 9 EC votes); VA (53%, 13 EC votes); IA (67%, 6 EC votes); NH (67%, 4 EC votes); OH (74%, 18 EC votes)
If Romney wins all the states currently leaning Obama except OH (4 of 5), he would still fall 2 Electoral College votes short.
If Romney wins OH, he would need to win 17 more Electoral college votes, possible with any number of combinations of the remaining states.
If Romney loses his own weakest leaning state FL; Romney could win all of the weak leaning Obama states and still not reach 270.
It all comes down to Ohio and Florida again!
If Romney wins Ohio, Obama has to hold both VA and CO to win.
If Obama wins Florida–Romney has to win OH, VA, WI, CO, NV, IA, NH