(CNN) First things first: The theme song of the week is the theme to "Will & Grace," by Jonathan Wolff.
Polls of the week: A Quinnipiac poll of New York's upcoming Democratic gubernatorial primary has Gov. Andrew Cuomo leading Cynthia Nixon 59% to 23%.
Cuomo's lead increased from Quinnipiac's last poll, which had Cuomo up 50% to 28%. It's the eighth poll of the race overall that has Cuomo ahead of Nixon by at least 20 percentage points.
What's the big idea: This race was supposed to be a marquee match-up for the left wing of the Democratic Party. Cuomo has a history of siding with Republicans in the state Senate, and the state's progressive Working Class Party backed Nixon. It would have been the capstone for progressives after Democratic socialist Alexandria Ocasio-Cortez defeated New York's Rep. Joe Crowley in a primary in June.
The left, though, hasn't been able to make a dent in Cuomo. His current margin over Nixon is actually larger than his margin over progressive challenger Zephyr Teachout in the 2014 Democratic primary for governor.
Cuomo's large lead is emblematic of two important trends in the Democratic Party.
The first, and perhaps most obvious, is that progressives look likely to fail in their biggest 2018 tests in the two biggest blue states. Besides Cuomo, Sen. Dianne Feinstein of California looks to be on her way to victory against Kevin de Leon. As with Nixon, progressive activists have endorsed his campaign. Voters overall, though, have a different perspective. Feinstein ended up 32 points ahead of de Leon in June's top-two primary. She also holds a large lead over him in general election polls.
While the #resistance is strong in both states, neither is a haven for the left wing of the Democratic Party quite yet.
The second trend is that Cuomo's lead is indicative of is the continually poor showing by progressive insurgents among black voters.
Cuomo is leading across pretty much all demographic groups, but he's particularly strong among African-Americans. Although no crosstab of black voters was available in the Quinnipiac poll, an earlier Siena College poll put Cuomo's margin over Nixon among black voters at 74% to 17%.
His advantage among black voters is no fluke.
When Ocasio-Cortez was cruising district-wide, she was weak in black neighborhoods. She was able to win in large part because of strength in areas with larger white populations.
Progressive Daniel Biss lost the Illinois gubernatorial primary earlier this year at least partially because he ran weak in the black neighborhoods of Chicago.
In 2016, Sen. Bernie Sanders, a Vermont independent who caucuses with Democrats, could never quite overcome Hillary Clinton's connection with black voters. She won them in New York by 50 points, for example.
Even for Cuomo, a black base is nothing new. When he beat Teachout four years ago, he did best in areas that were predominantly black.
Of course, Ocasio-Cortez was able to win overall anyway. That wasn't the case for the progressives in the other examples, though. It's tough for progressive challengers to win when they lose by 50 points among a group who make up more than a fifth of the electorate.
Why are progressive insurgents struggling with black voters? Black Democrats are more likely to consider themselves moderate or conservative than other Democrats. They also are more likely to identify as Democrats instead of independents who lean Democratic.
That is, they are far more comfortable with the more moderate Democratic establishment than other Democrats are, especially whites.
Now obviously it's possible for progressive challengers to win a primary even with this difficulty (see Ocasio-Cortez). But until candidates like Nixon and Sanders solve their black voter problem, they're going to be limited in their electoral victories.