I'd say most of them, if not all. However, I decided to do me some research, and I can now pinpoint the switch.
1964.
The previous election was fairly moderate accross the board. 1960 was focused more on the cold war than civil rights, so it ended up being about money and space - not very informative. '64 was the decisive switch. Since liberals - namely Republicans at the time - supported civil rights, Republican candidate Goldwater did the wrong thing - he spoke against it. He said that civil rights - namely desegregation - was a states rights issue, not federal (note states rights now being a common theme among modern Republicans). This turned away the liberals to the Democratic Lyndon B. Johnson. Hop forward to 1968, and Republican Nixon sweeps into office.
Where does Nixon fit in, you ask? Well, his 'Southern strategy' is where. He appealed to whit southern voters, who 'who traditionally voted Democratic, but were opposed to Johnson and Humphrey's support for the civil rights movement'. This is the definitive switch from liberal to conservative in the Republican party.
Hop forward again, 1972. We've seen the Republican switch, so how about the Democrats? Well, besides obvious civil rights, liberals are also fairly anti-war (though that seems to be shifting today, so don't expect that to hold true for too much longer). We also like to support the little guys, especially the poor. Enter George McGovern, the Democratic candidate of 1972. Strictly against Vietnam and planning to institute a guaranteed minimum income for the poor, he was denoted as a left-wing extremist and, to put it bluntly, got his ass handed to him by Nixon. You see these similar themes against fighting and helping the poor continue to appear in liberal, and thus democratic policies (though, again, the anti-war stuff is on the way out).
'76 is fairly lackluster, though it shares some parallels with this year's election, and if your interested go ahead and look it up, but it doesn't contribute anything here, and I would like to remain on topic.
1980. This is the year when everything is officially recognized. In fact, it is called by some the 'realigning ellection'. Nixon's conservative success as a Republican caused many liberal Republicans to leave and and conservative Democrats to join the Republican party (obviously, the exact opposite happened to the Democratic party).
TL;DR, they switched on everything.