The rules of the electoral college state that the President must be chosen by a majority (read as a simple majority) of the total number of available electors in a Presidential election. It stipulates conditions for what to do in the event no single person holds a majority (thus implying that all electors includes the electors that were up for grabs but did not vote for either runner... The founders had conceived this because they expected faithless electors). Should your four states not submit any electors, then they essentially do not vote, but they still count for securing the majority, meaning 270 is still the number to beat (Article II).
Should this happen, it automatically triggers a contingent election in the House and the Senate, with the House picking the President and the Senate picking the Vice President. The House pick is unusual in that under current law, the House selects the President with one vote per state delegation (rather than one vote per representative) with each state's total representatives meeting and voting on which candidate gets that state's vote. So the majority control of the house is not a bellweather for who the president is. In 2021 (when this vote happens) the House will be Democrat majority, but of the state delegations Republicans have the majority (More State Delegations are 51% or more Republican than are not).
In the Senate, because the states are equally represented, the Vice President is picked by simple majority vote.
A Quorum of 2/3rds of the senate and 2/3rds of the states by any number of it's representatives must be in the vote (so if the Democrats tried to walk out of the House, the vote still proceeds... if a state is 7 dems to one republican, and all 7 walk out, the Republican may still cast a vote for his/her state so the quorum is unaffected. Right now there are only about 5 states that are solidly one party in it's delegation.).
A contingent election can also be triggered by one member of the House and one member of the Senate challenging any number of states' electoral votes, at which point there is a 2 hour debate followed by a vote to remove any state's electoral submission that has been so challenged. IF they remove enough that no candidate has 270, then the contingent election rules apply.
These two rules are governed under the Electoral Act of 1877, which was brought into law following the troubled election in 1876. Because no election since has been this close to a challenge, the Act has yet to be invoked and there is some legal debate if the act is binding only on the Congress that passed it or if it's binding law on subsequent congresses. If the latter, than the contingent election rules may not apply and this explanation may be tossed out.
Just a quick general timeline.
First Tuesday after the First Monday in November: General Elections. States who select electors based on popular vote (all of them) vote on this day.
November-early December: Votes are tallied, the results certified, and the Electors selected. Election Contestations may be filed once the results are certified in those states which allow it.
December 6 days before the Electoral College meets to vote: Safe Harbor - All states that have resolved their election contests and certified their elections are garenteed to be counted by the Electoral College. Those that have not can still resolve by the EC Meeting date, but are not garenteed to be admitted (The EC can choose to admit them or choose to exclude them).
Early December: EC meets to vote. All votes are tallied and sealed in an envelop and transmitted to the chief archivist of the United States.
December-January: Generally the Christmas Holiday season. Congress takes a break while support staff remove the furniture from offices of ousted congressmen/women and bring in the new guy's stuff.
January 2nd: The new congress meets and begins parliamentary proceedures (picking leadership positions and other matters).
Early January (Few days after new congress meets): Archivist transmits the envelop to the Incumbent Vice President of the United States, who reads the results in a joint session. Any challenges from Congress are resolved and a failure for any candidate to capture a majority of the vote will result in a contingent election, which immediately happens. Either way, by days end, the President elect is declared.
Jan 20th: The President-Elect becomes the President at 1200 EST. If this date falls on a Sunday, this still happens but the festivites in D.C. (including a public swearing in ceremony) take place on the 21st (tradition, not law, so as not to disrupt the Sabbath. Assumption of office can take place rather quickly so the nation does not have a sucession crisis.).