The Democrats don't really support the working class. It's a common misconception as we generally equate them with other labour movements around the world eg. ALP or the Labour Party in the UK.
The Democrats don't really have that background as labour movements in the US were violently supressed and shut down by most extant political organisations. So while people like Bill Shorten have genuine ties to unions and the 'working class', it is a hit different than the Democrats.
The Democrats have always, and will always, care more about big corporations than they do about the working class.
That's a pretty big and misleading stretch. The Democrats and the Republicans 'swapped' in the 20th Century, so of course they don't have history to show for it, but that swap was related to the 'New Deal' after the Depression, which brought about a more 'left-wing' social contract that we would associate more closely with European/Commonwealth Democracies. From Wiki (my bold):
These programs included support for farmers, the unemployed, youth and the elderly as well as new constraints and safeguards on the banking industry and changes to the monetary system. Most programs were enacted between 1933–1938, though some were later. They included both laws passed by Congress as well as presidential executive orders, most during the first term of the
presidency of Franklin D. Roosevelt. The programs focused on what historians refer to as the "3 Rs":
relief for the
unemployed and poor,
recovery of the economy back to normal levels and
reform of the financial system to prevent a repeat
depression.
The New Deal produced a political realignment, making the Democratic Party the majority (
as well as the party that held the White House for seven out of the nine presidential terms from 1933–1969) with its base in liberal ideas, the South, traditional Democrats, big city machines and the
newly empowered labor unions and ethnic minorities. The
Republicans were split, with c
onservatives opposing the entire New Deal as an alleged enemy of business and growth and liberals accepting some of it and promising to make it more efficient. The realignment crystallized into the
New Deal coalition that dominated most presidential elections into the 1960s while the opposing
conservative coalition largely controlled Congress from 1939–1964.
Roosevelt created a large array of agencies protecting various groups of citizens—workers, farmers and others—who suffered from the crisis and thus enabled them to challenge the powers of the corporations. In this way, the Roosevelt administration generated a set of political ideas—known as New Deal liberalism—that remained a source of inspiration and controversy for decades. New Deal liberalism lay the foundation of a new consensus. Between 1940 and 1980,
there was the liberal consensus about the prospects for the widespread distribution of prosperity within an expanding capitalist economy.[123] Especially
Harry S. Truman's
Fair Deal and in the 1960s
Lyndon B. Johnson's
Great Society used the New Deal as inspiration for a dramatic expansion of liberal programs.
I don't mind being wrong, as I'm not a strong scholar on this, but here's
more evidence for strong unions in this time from The Atlantic:
The New Deal era of the 1930s through the 1970s was largely defined by high and rising wages, which were pushed up by
strong unions, limited global competition, low energy and commodity prices, and more stringent regulations on businesses...
...But...many employers—led by industrial giants like General Motors and General Electric—acted as “welfare capitalists” that were also primarily responsible for providing benefits like a pension to workers and their families. Part of the motivation was cultural: Before the notion of shareholder capitalism took root in the 1980s, companies viewed it as part of their mission to act in the interests of all of their stakeholders, including workers and their communities, rather than in the interests of investors alone.
However, companies also favored the arrangement because providing benefits to workers directly gave them some leverage against labor unions. Ultimately, the welfare-capitalist social contract became the norm.
So the seeds were there for the way America would become. Still, Roosevelt's vision was successful enough that it created a consensus, and it can still be said (as Wiki comments), that the power break-down in that time was very much Democratic:
1933-1945 Franklin Roosevelt Democratic - congress with him for basically all of his 12.1 yrs. He then died.
1945-1953 Harry Truman Democratic - congress with him for 6 of 7.8 yrs. There were complaints about strikes (labour power) early in his time in charge, though, and he became anti
some Unions. Congress went Republican in 1946 (Nixon and McCarthy were freshmen), and passed the Union-limiting 'Labor Management Relations Act', which Truman vetoed, but Congress overrode that. Democrats won it back in 1948 with Truman saying he would repeal the act, but southern Democrats didn't allow it. That's a familiar problem still stopping progress on issues in today's America - 'the South', politically, are fairly right-wing. Truman's 2nd win was a surprise. Democrats even tried to recruit a replacement for him beforehand. That man was:
1953-1961 Dwight Eisenhower Republican - congress with him for only 2 of 8 yrs.
1961-1963 John Kennedy Democratic - congress with him for all of his 2.8 years. He was then assassinated.
1963-1969 Lyndon Johnson Democratic - congress with him for all of his 5.2 years.
Nixon is then elected, showing how the narrative of America politics had gone in a different direction. Tricky Dicky was a paranoid guy, and keen to tell Americans they too were being left behind by others (Goldwater saw the power of that narrative).
But the Democrats still had both houses, and would do so up until Reagan's election, when we saw that 'neo-liberal' thing really take hold in America. The Democrats would then not win the Presidency for 14 years, until Clinton did his 'centrist' pitch, which as we know, was still corporation-friendly. As with all the 'Bernie would've won' claims, people willfully ignore the political reality of America (more often that happens in order to pretend the Democrats are similar to the Republicans). The Democrats didn't win power until they moved closer to the Republicans. They did more for the poor (like Obama did), but they didn't legislate a drastic change to America like Roosevelt did in the New Deal and like Reagan reversed in the 80s.
The narrative may have changed again now, thanks to Bush's incompetence and the GFC highlighting just how much America's economic policies were failing (at a macro level to match their failures at a micro level for so many), but the vote for Trump was still significantly right-wing in nature, so we can't be sure yet. It looks like Don Don has done enough to ensure the narrative has shifted, but of course his fans and the right-wing media will continue claiming otherwise (e.g. their gun control propaganda), so it's hard to predict. Information warfare is a real issue here.
This is already too long, but anyway, here's a quote from Eisenhower which references 'labor laws', to show where he was coming from as the Republican in that 36 year run listed above. It also shows that back then it was Republicans having to accept the political reality of American voter's opinions:
Now it is true that I believe this country is following a dangerous trend when it permits too great a degree of centralization of governmental functions. I oppose this — in some instances the fight is a rather desperate one. But to attain any success it is quite clear that the Federal government cannot avoid or escape responsibilities which the mass of the people firmly believe should be undertaken by it. The political processes of our country are such that if a rule of reason is not applied in this effort, we will lose everything — even to a possible and drastic change in the Constitution. This is what I mean by my constant insistence upon “moderation” in government. Should any political party attempt to abolish social security, unemployment insurance, and eliminate labor laws and farm programs, you would not hear of that party again in our political history. There is a tiny splinter group, of course, that believes you can do these things. Among them are H.L. Hunt (you possibly know his background), a few other Texas oil millionaires, and an occasional politician or business man from other areas. Their number is negligible and they are stupid.
Also, for what it's worth:
Eisenhower's cabinet, consisting of several corporate executives and one labor leader, was dubbed by one journalist, "Eight millionaires and a plumber
tl;dr Democrats do have history of being pro-working class people.