It's a matter of very serious dispute if you were to read people who are actually on the left, or who live outside the USA.
The stated policies of the US Democratic Party barely correspond to those of leftist parties worldwide. Their actual policies when in power are even further from those of leftist parties worldwide.
So .. are they left of the US Republican Party? No question. Are they "on the left" in any broader sense? That depends very much on your conception of the nature and scope of the political space. For most people in most parts of the world, the US Democratic Party is a completely centrist party that would never be termed "leftist".
> It's a matter of very serious dispute if you were to read people who are actually on the left, or who live outside the USA.
Ah, that old standby "No True Scotsman". Sorry, not buying it.
> The stated policies of the US Democratic Party barely correspond to those of leftist parties worldwide.
No political party's stated policies can be taken seriously, since political parties, on immense amounts of historical evidence, will lie about their actual goals as much as they need to to get elected and stay elected.
For example, the Democratic platform that FDR ran on in 1932 did not look very leftist, but the actual things he did once in office were most definitely leftist, and bore no resemblance whatever to the platform he ran on. Did any Democrats object? Hollow laugh.
If you want to argue that the US Democratic party is not as far left as, for example, leftist parties in the UK or Europe, yes, that's probably true. But saying that that means the US Democratic party is not leftist is like saying that the Atlantic Ocean is not an ocean because it doesn't have quite as much water in it as the Pacific.
If you seriously think that the US Democratic party, as compared to leftist parties in Europe, is closer to Walden Pond than the Atlantic Ocean in terms of leftism, then you and I clearly live on different planets and we don't have enough common ground to have a useful discussion.
In fact, historically speaking, even the US Republican party today is closer to the Atlantic Ocean than Walden Pond in terms of leftism. What today's US Republicans consider "conservative" would have been considered so far left as to be radical to the US Republicans of the late 19th century.
> A party that overtly supports capitalism is not a leftist party.
I'm not sure how the US Democratic party "overtly supports capitalism", since it is the party of government micromanagement of every aspect of business.
I'm also not sure how leftism is inconsistent with support of capitalism, unless the latter is taken to imply a complete rejection of socialism. Which is certainly not a good description of the US Democratic party. To the extent it does "support" capitalism, it is only as one aspect of a society which the party wants to organize along mostly socialist lines.
Americans have little knowledge of their history, can't imagine an era when there were actual socialists, marxists, communists, fascists and literal nazis in uniforms holding conventions in NYC.
You mean the GOPs modern definition of a leftist, or the vast majority of the times definition of a leftist?
https://encyclopedia.densho.org/Norman_Thomas/