Each candidate needs at least 270 electoral votes to win outright, and a tie at 269 that throws it into the House isn't impossible.
Obama | McCain
Votes Probability | Votes Probability
268+ 0.9894 | 268+ 0.0129
269+ 0.9887 | 269+ 0.0121
270+ 0.9879 | 270+ 0.0113
271+ 0.9871 | 271+ 0.0106
272+ 0.9863 | 272+ 0.0099
273+ 0.9854 | 273+ 0.0093
274+ 0.9844 | 274+ 0.0087
275+ 0.9834 | 275+ 0.0082
280+ 0.9774 | 280+ 0.0058
285+ 0.9693 | 285+ 0.0041
290+ 0.9585 | 290+ 0.0028
295+ 0.9443 | 295+ 0.0019
300+ 0.9260 | 300+ 0.0013
305+ 0.9025 | 305+ 0.0009
310+ 0.8727 | 310+ 0.0006
315+ 0.8365 | 315+ 0.0003
320+ 0.7929 | 320+ 0.0002
325+ 0.7418 | 325+ 0.0001
330+ 0.6831 | 330+ 0.0001
335+ 0.6193 | 335+ 0.0000
340+ 0.5498 | 340+ 0.0000
345+ 0.4767 | 345+ 0.0000
350+ 0.4037 | 350+ 0.0000
355+ 0.3322 | 355+ 0.0000
360+ 0.2648 | 360+ 0.0000
365+ 0.2025 | 365+ 0.0000
370+ 0.1507 | 370+ 0.0000
375+ 0.1075 | 375+ 0.0000
380+ 0.0730 | 380+ 0.0000
385+ 0.0486 | 385+ 0.0000
390+ 0.0314 | 390+ 0.0000
395+ 0.0198 | 395+ 0.0000
400+ 0.0123 | 400+ 0.0000