The Democrats abandoned the working class decades ago. Of that there is no doubt.
But it's only since 2016 when the divide between the party leadership and the base gotten so large and obvious that it can be measured.

For starters, let's look at what has changed with the voters.

According to Pew data, 46 percent of Democrats and Democratic-leaning voters now identify as liberal—up from 28 percent 10 years ago. Meanwhile, the percentage who say they’re moderates has dropped from 44 to 37. The number of conservatives continues to drop, too.
...
On economics, three-quarters of Democrats say that the government doesn’t do enough to help poor people, up from half in 1994. Two-thirds say that government should regulate business more, again up from half in 1994. Conversely, in 1994, two-thirds of Democrats believed that people could get ahead if they were willing to work hard. Now only half do. The percentage of Democrats who believe that corporations make too much money is up 12 points. But the movement is not uniform. While the portion of Democrats who say that the government should do more to help the poor, even if it requires taking on debt, rose from 58 percent in 1994 to 71 percent in 2017, it is still below the peak of 77 percent, in 2007.

The poll also shows how the base has shifted left on social issues, but since these issues don't cost anything monetarily, the Dem leadership actually tries to represent on these issues.

Now let's look at the candidates.

In the most competitive House races, particularly in districts that lean toward Republicans, researchers at the Brookings Institution ran the numbers and concluded that Democrats are relying more on moderate candidates in those districts over self-identified progressives.
“The steady success of establishment candidates calls into question whether the Democrats are being pulled to the left,” researchers Elaine Kamarck and Alexander Podkul wrote.

A different data set points to the same conclusion: In the 69 most competitive House districts, only 15 Democratic candidates have endorsed Medicare-for-all, the policy pillar of the left’s enthusiasm, according to an analysis by Forbes-Tate, a DC-based lobbying firm.

The neoliberal centrism is even more pronounced in the Senate.

Sen. Claire McCaskill (D-MO) ran a recent radio spot that says, “Claire’s not one of those crazy Democrats. She works right in the middle and finds compromise.”
Sen. Joe Manchin was the only Democrat to vote to confirm Brett Kavanaugh to the Supreme Court (though he wasn’t the deciding vote) and looks like he looks like nearly a lock for reelection going into Election Day.
Democrats have an unexpected chance to win a Senate seat in Tennessee thanks to the state’s lingering fondness for moderate ex-Gov. Phil Bredesen, a Democrat who cut Medicaid as governor and who says he would have voted for Kavanaugh’s confirmation if he had been in the Senate.
Democratic nominee Kyrsten Sinema is playing to the middle for retiring Sen. Jeff Flake’s seat — in spite of some well-documented flirtations with the left — in her Senate campaign against Republican Martha McSally. She’s highlighted that she voted with Trump 60 percent of the time, one of the highest rankings among House Democrats.

More incumbent Democrats faced primaries—45 percent, up from fewer than 28 percent in 2014. Most of these challengers were progressives.
Almost all of the challengers lost. Part of the reason for the lack of success is things all challengers face, such as lack of name recognition.
A bigger reason is that the progressive insurgents didn't take corporate money, and thus were overwhelmed by cash.
And then, of course, there was the establishment advantage.

The Democratic establishment may think they've won something by defeating the progressives this time around, but what sort of political party feels good about silencing and disenfranchising their own voters?
That's a political party headed for oblivion.