It is basically impossible, but let's say the candidates in a state both get 3,454,573 votes or something. Who does the state go to and how is it decided? This has always bothered me, especially since it came so close to happening in Florida and New Mexico in 2000.
In Missouri, electors are elected by congressional district based on the statewide vote. In case of tie, the legislature determines the elector from each district.
In the past, some states have required majority election for electors. In those cases, the legislature chose the electors, but there is nothing in the constitution that would preclude a runoff.
