I address this question in a new article for the British site, Unherd. I argue that the Democratic party is indeed moving left but not in the fashion envisioned by self-conscious radicals like Alexandria Ocasio-Cortez.
"The Left in America is on the rise...But how far Left is this surge? And what does it stand for? Can it really be compared with the hard Left radicalism seen elsewhere across the globe?
Rhetorically, this new Leftism rejects ‘business as usual’ and involves a sweeping indictment of the economic and political system for generating inequality and doing little to help ordinary people in the wake of the great financial crisis. Substantively, Democrats today – in particular aspirants for the 2020 Democratic Presidential nomination – are far more willing to entertain and endorse ‘big ideas’, such as going beyond the ACA, aka Obamacare (which is now vigorously defended) to ‘Medicare for all’, free college education, universal pre-kindergarten provision, vastly expanded infrastructure spending and even a guaranteed jobs programme. Taxing the rich is ‘in’ and worrying about the deficit is ‘out’.
Democrats are also highly unified on core social issues such as opposing racism, defending immigrants, promoting LGBT and gender equality and criminal justice reform. In short, the centre of gravity of the Democratic party has decisively shifted from trying to assure voters of fiscal and social moderation, to forthrightly promising active government in a wide range of areas.
But this hardly means the Democrats are in any danger of becoming a radical party. Far from it. As Leftism goes, the current Democratic iteration is of a fairly modest variety, approaching, at most, mild European social democracy. Those who call themselves ‘socialist’ (as Ocasio-Cortez does) are few and far between.
Nor is it the case that incumbents and moderates are being thrown out wholesale and replaced with candidates much farther to their Left. Across the country, only two Democratic incumbents in the House lost primaries, and none in the Senate did. A Brookings study found that self-described “progressive Democrats” did well in primaries this election season but establishment Democrats actually did somewhat better. Thus, the change in the party is less a Leftward surge featuring new politicians (though this is happening to some extent) and more a steady party-wide movement to the Left."
That's my take. Read the whole article for more detail.