We have debated this at length. My congressional sources think that the number is 270, period. Not a majority of those submitted.
The enabling legislation for the Constitution does not allow for the non-submission of an electoral slate. We have never had this happen. In 1860, the South submitted its electors, then seceded when the wrong guy won, but the electors were in.
In 1876, the electors were sent in, but contested.
Apparently the 1887 legislation said that when there was a conflict between two sets of electors, the governor chose. I seem to recall more recent legislation, however, that put it back in the hands of the state legislature. I could be wrong.
At any rate, I don’t think you can just have a state “not submit.” If not in on Dec. 14 to the Senate, the US Senate can demand the slate; the US Archivist will demand the slate; and a state court can demand the slate. The law is mum on what happens if these demands are not met. There is a PENALTY ($1,000.00) for the PERSON (i.e., I guess the Sec State) who doesn’t deliver the slate to the Senate, but I cannot find any penalty for any state that doesn’t submit. Therefore, I see no enabling legislation that says that you can have a majority less than 270.
There's been some serious foolishness with this "it goes to 260" nonsense.