Kennedy won both narrowly in 1960. In 1964, they were both a few points more GOP than the nation as a whole. Then in 1968, Nixon won both by convincing margins (8% points in NV and 12% points in NM).
What happened? What caused these states to trend Republican?
Republican presidential realigning election of 1968.
Now that the opposite is the case with both states…
Democratic presidential realigning election of 2008.
Nevada and New Mexico have long-established that they are presidential bellwether states with voting electorates which trend with the nation.