I don't know for certain. Statutory law doesn't address this issue, but common law might. The two likeliest interprestations are that either:
- all four candidates would be under consideration, or
- before proceding to the election of a president, the House would first have to determine which three candidates that it wished to consider.
The problem is extremely unlikely to coccur, and it certainly won't happen this year. It might come up in 2008. If the Coloradao initiative passes, a 268-268-1-1 result is not at all impossible and would provide a reasonably sane and safe way to test what to do.