I agree with your assumption of 257. Now, if that’s the case, Romney has at least three paths to cover the rest 13 EV:
1. OH (18)
2. NV(6)+IA(6)+ME(1)
3. WI(10)+ NH(4)
Note that each of the option is mutually exclusive from the others. Each shows RR needs to work very hard.
That could really be WI and any other full state.
Also note if he gets option 2 without ME’s vote, it’s a 269-269 tie. Which means Romney will be voted in as prez by the House easily but Biden could be voted in as V.P. by the Senate. Good thing Romney said he liked bipartisanship.
That “tie” scenario is also identical to the 2004 results except giving the Dems NM and OH.
If NV is a lost cause as some have suggested, then IA(6), NH(4), and ME(1) leaves Romney one EV short of a tie (270-268). Romney really needs one of OH or WI to make it work without NV.