1988 election between Bush and Dukakis California voted for the Republican candidate.
In 1988, California usually voted for the Republican candidate. In fact, except for 1964, California voted Republican in every presidential election from 1952 to 1988. However, with the end of the Cold War, many of the conservative defense industry companies became much smaller or closed. Environmentalism became a much bigger issue. Also, the demographics have shifted.
1976 election between Carter and Ford Texas voted for the Democratic candidate and California voted for the Republican candidate.
As I said, that was as expected for California. Similarly, Texas had been a reliably Democratic state since the Republican party had been in existence. It was more odd to see it voting Republican for President in 1952, 1956, and 1972. Reagan turned it permanently Republican at the presidential level, but prior to 1980, it was usually a Democratic state.
Even after 1980 Texas continued to vote for conservative Democrats for governor, Senator, and Representative. For example, conservative stalwart Rick Perry was a Democrat when he first entered politics.
1964 election between Johnson and Goldwater Texas, Utah, Idaho all voted for the Democratic candidate.
And in 1972 every state except Massachusetts and the District of Columbia (DC) voted for Nixon. In 1984, every state except Minnesota and DC voted for Reagan. From 1932 to 1944, landslides for the Democrat were routine.
Of course, in 1932, Franklin Delano Roosevelt ran as the conservative alternative to Herbert Hoover. That seems unlikely today.
Richard Nixon would describe himself as a liberal when he ran, much as Bill Clinton ran as a conservative.
Recent years have seen a strong increase in partisanship of policies. That used to be less common. New England Republicans were liberal in policy. Southern Democrats were conservative. Modernly, every Democrat is more liberal than every Republican. Even Heidi Heitkamp and Joe Manchin are on average to the left of Susan Collins, although they are on the Republican side of her on some issues.
There are no remaining New England Republicans. Susan Collins is the only Republican New England Senator, and she is not as liberal as her predecessors.
There are no remaining Southern Democrats. The deep South states all have two Republican Senators. There are some Representatives, but they tend to be in majority minority districts.
Only eleven states have split Senators (one Republican; one Democrat). Two more states have one Democrat and one independent, but both independents caucus with the Democrats. Nine of the Democrats who serve a state with a Republican Senator are up for reelection in 2018. One was elected in 2016 and the Republican is up in 2018 (in Nevada). Colorado is the only split state where neither is up in 2018.
On policy, opinions have hardened.
Of course, that could change in a single election. The two Georges Bush have been the only Republican presidents since Reagan. Neither was that popular at reelection time. Perhaps Donald Trump reassures his critics with his actual governing and wins reelection in a landslide. Or not. Note that he almost won Minnesota, which apart from the District of Columbia has the longest streak of voting for the Democratic presidential candidate.
At one point, people thought that Hillary Clinton might have had a bigger landslide victory than Obama, winning Arizona, Texas, and Georgia. Those three states consistently voted against Obama.
It's easy to perceive a streak where actually there is only coincidence. Three Republican presidents were reelected in landslides. Then two weren't. A coin has a one in eight chance of coming up tails three times in a row. That's not nearly rare enough to prove that that was a meaningful streak.
Obama is the only Democrat to win a majority of the popular vote since 1976, although the Democrat has won at least a plurality in six of the last seven elections (1992-2016; only falling short in 2004). Republicans won five of six elections from 1968 through 1988. From 1896 through 1928, Republicans won seven of nine elections. And then lost five in a row from 1932 through 1948. Long streaks are normal.
Starting in 1952, the presidency has switched every eight years, except it switched early in 1980 and and stayed with the Republicans through 1992. Other than that, Democrats and Republicans have alternated the presidency. Maybe that's luck. Maybe that's a result of an electorate that wearies of parties every eight years.