I beg to differ, Argent. Adlai Stevenson is VERY relevant. He represented what the Democratic party was becoming, and what George McGovern institutionalized.
As the OP notes, “liberals” used to be tougher, in large part because the Democratic party was positioned as the party of working class Americans. Blue-collar urban Catholics and Southern rednecks were the backbone of the Party until relatively recently. And THOSE voters were interested primarily in the economic benefits that activist government could provide. They voted a straight Democratic ticket, and they were “liberals” in the sense that they backed the New Deal and wanted the rich to cough up a bigger share of the pie.
But they were NOT liberals in any social sense. They were religious, they supported traditional family values. Nor were they pacifists on foreign policy. They generally believed in a very strong military.
As long as THOSE people were the backbone of the Democratic party, liberals could look and talk tough.
But even in the Fifties, there were elements in the party that held blue collar whites in disdain, and wanted to dump them. Adlai Stevenson was their ideal candidate. Not surprisingly, blue collar whites had no use for Stevenson, and flocked to Ike.
To people on the far Left of the party, that only PROVED that the party had to be rebuilt, that the blue collar whites had to be pushed aside and replaced by college educated social liberals and pacifists. Ideally, they hoped, some of the white working class could be bribed to stay part of the coalition… but Fred Dutton, George McGovern and friends completely remade the party in their mown image.
After 1972, Democratic party liberals de-emphasized the issues that mattered to blue collar America, essentially DRIVING much of their base to vote for Ronald Reagan.
In the meantime, liberals have learned that wasn’t a winning strategy. So, they’ve had to campaign by stealth. In SOME states, liberal Democrats can state openly what they support and win elections. In other states, they still CAN’T win without blue collar whites. In those states, they have tor straddle. They may personally support gay marriage, but find it expedient to say nothing on the issue, and hope the Supreme Court takes the decision out of their hands.
It all comes down to this: “liberal” today means something much, much different from what it meant under FDR.