The problem with this is that a small state which does it makes itself worth less to a presidential candidate. It also renders "swing states" impotent because candidates will know that they can always win a number of electoral votes from these states, instead of having to campaign hard to win all of the electoral votes from them.
The current system of electing the president ensures that the candidates, after the primaries, do not reach out to all of the states and their voters. Candidates have no reason to poll, visit, advertise, organize, campaign, or care about the voter concerns in the dozens of states where they are safely ahead or hopelessly behind. The reason for this is the state-by-state winner-take-all rule (not mentioned in the U.S. Constitution, but now used by 48 states), under which all of a state’s electoral votes are awarded to the candidate who gets the most votes in each separate state.
Presidential candidates concentrate their attention on only a handful of closely divided “battleground” states and their voters. In 2008, candidates concentrated over two-thirds of their campaign events and ad money in just six states, and 98% in just 15 states (CO, FL, IN, IA, MI, MN, MO, NV, NH, NM, NC, OH, PA, VA, and WI). 19 of the 22 smallest and medium-small states (with less than 7 electoral college votes) were not among them. Over half (57%) of the events were in just four states (Ohio, Florida, Pennsylvania and Virginia). In 2004, candidates concentrated over two-thirds of their money and campaign visits in five states; over 80% in nine states; and over 99% of their money in 16 states, and candidates concentrated over two-thirds of their money and campaign visits in five states and over 99% of their money in 16 states.
Two-thirds of the states and people have been merely spectators to the presidential elections.