Creepy Uncle Joe is the ultimate insider of the Democratic Party establishment, so when he endorses someone you know that he's not doing you any favors.
So who has Biden endorsed? Darren Soto is one.
Soto is notable for only one thing - who he's running against.

Former Vice President Joe Biden, a possible presidential candidate in 2020, took sides in one of the most competitive Democratic congressional primaries in the Sunshine State.

On Tuesday, Biden endorsed U.S. Rep. Darren Soto, D-Fla., for a second term in Congress over former U.S. Rep. Alan Grayson, D-Fla. In 2016, Grayson ran for the U.S. Senate but was routed in the Democratic primary by then U.S. Rep. Patrick Murphy, D-Fla., while Soto defeated a field of candidates--including his current rival’s wife Dena Grayson--to win the open seat.

The Congressional Progressive Caucus Political Action Committee came out in support of Soto.

Soto has the endorsements of every single member of the Florida Democratic Congressional Caucus.

Nancy Pelosi also didn't want Grayson to run.

"But Darren is there now and is very important to us in terms of generationally and also in terms of issues that relate to Puerto Rico, which are a priority for us to address. I have supported Darren Soto. I'm sad that Alan chose to come back in that race.

It sounds like Grayson is an unpopular candidate running against a popular progressive candidate.

Looks are deceiving.

He has an adoring national progressive base, with more than 100,000 campaign donors. He passed more legislation than any other member of Congress. Grayson also has a lot to show locally for his time in office, like the VA Hospital, the extension of SunRail, and big increases in federal funding in his district.
...
In 2016, Soto squeaked by in a four-way primary, with just 37% of the vote against three opponents who had never run for office before. Soto isn’t a fundraising lightweight, though. He notched over $400,000 last year, 65% of it from corporate special interest PACs, and he continues to raise money.

If Grayson challenges Soto, it would be an interesting race to watch. One website said that a poll showed Grayson 65%, Soto 35%, but it wouldn’t necessarily be an easy win for Grayson. Soto had many conserative positions in the Florida Legislature, drawing an “A” rating from the NRA and voting for “docs vs. Glocks,” a $200 fee from women seeking protection from domestic violence and mandatory ‘transvaginal ultrasound’ for women seeking an abortion.

Firstly, Soto is anything but a progressive. His conservadem credentials will not inspire the base.
Secondly, it looks like another case of the Dem establishment trying to shove a centrist candidate down throat of it's progressive base.

Finally, I looked and failed to find a single poll on this race. Which is a curious coincidence when I looked at Biden's other major Democratic primary endorsement.

Over on Long Island, Biden, who spoke for about 45 minutes—much longer than Clinton, who clocked in at 12 minutes—pointed to Cuomo’s achievements such as paid family leave, marriage equality, a statewide $15 minimum wage and tougher gun laws.

“Andrew Cuomo has never backed away from his progressive principles, not one single time,” Biden argued.

I've already gone over Cuomo's questionable "progressive" credentials.
However, I couldn't help but notice the lack of recent polls in the NY governor's race.

So Nixon starts out way behind, then cuts the lead in half in just a month, and then...not a single poll in six weeks?!?!
WTF?
Are we simply not doing polls in primaries where establishment candidates might lose to progressives?