The people you're going to need to win over in the General Election are Independents & new/younger voters (The Groups That Already Make Up Bernie's Base). Bernie has shattered records with small individual donations validating his grass roots support. Biden may have edged it out (Disregarding Primary Election Fraud). Biden won 70% of voters age 45 & older, while Bernie won with the 18-45 age demographic also with 70%. Despite Biden getting the slightly bigger group in the primary, only Bernie gets both of those groups in the General making Bernie the only electable choice.
Both Bernie & Biden will already get most of the older Moderate Democrats in the General, but that one demographic can't win the General Election by themselves. Only Bernie will get the older Moderate vote (In The General), the youth vote, many new voters, independents, & even some cross over Trump & Republican voters. Not only would Bernie win, he would most likely win in a land side, the polling data more than backs this up. Not just with the massive number of small individual donors as I mentioned before, but look at the favorability ratings & polling data for further evidence.
ABC News/Washington Post
It's not just Bernie himself that is popular (Despite Multiple Polls Showing Bernie To Be The Most Popular Politician In The Entire Country) Bernie's policy platform is overwhelmingly popular with the majority of the American people. 57% want to break up the big banks, 58% want a $15 minimum wage, 60% want tuition free public colleges & universities, 64% want to legalize marijuana, 70% want Medicare-For-All, 72% want to expand Social Security, etc... etc...
The truth is Corporate Establishment Democrats don't win elections. This is why individuals such as Al Gore, John Kerry, Hillary Clinton, & now Joe Biden will always lose in a General Election. While a Democrat like FDR (Of Which Bernie Is A Similar New Deal Democrat) was so incredibly electable the Republicans invented term limits because they knew if they didn't they would never win the presidency for the rest of time. Now there are always a few exceptions to this rule, but there is good reason for those exceptions. For example Obama is a Corporate Establishment Democrat, but was able to win with all those Demographics I mentioned because Obama didn't run as himself, he ran as a Progressive. Obama attacked Hillary on things like the Iraq war & trade deals such as NAFTA. At the end of the day Obama kept us in Iraq & even ramped up the number of wars we were in to eight. Obama also kept us in NAFTA while pushing more Disastrous offshore trade agreements like the TPP. In fact the Neo-Liberal policies of Obama (Not Governing As He Campaigned) crushed/disenfranchised the American people so much they were willing to take a chance on Donald Trump in the first place.
Not only did these Neo-Liberal policies lead voters away from the Democratic Party, they left in numbers so great it caused the Democrats to lose the Presidency, they lost the majority of the Senate, the House, Governorships, State & Local offices, the Democrats got wiped out on every level of Government. Though thanks to Populist-Left Progressives, in the following Election the Democrats were able to win back the House. This was accomplished due to groups like Our Revolution, Brand New Congress, & Justice Democrats that ran Bernie Sanders style Democrats. This gave us Justice Democrats like "The Squad".
The Primary is actually the only real hard part for Bernie (The General Would Be The Easier Obstacle Than The Primary). As I mentioned a lot of Bernie's base is made up of new young voters & independents, many of which are excluded from the Democratic Primary due to voter suppression. One good example of Voter suppression is the Super Closed Primary in my home state of New York. If you wanna vote in the Democratic primary in New York, you not only have to be registered as a Democrat, but you had to register as far back as early February. That is a type of voter suppression which just doesn't exist in the General helping to make Bernie the strongest General Election candidate.
On top of that in the 2016 N.Y. primary the hours of polling places were changed. The polling places that heavily supported Bernie were shortened from 6:00 A.M. - 9:00 P.M. to 12:00 P.M. - 9:00 P.M. (Including My Own Polling Place) compared to the areas that supported Hillary more which kept their 6:00 A.M. - 9:00 P.M. hours. (I Was Lucky Enough That My Work Schedule At The Time Freed Me Up To Vote That Day, Many Others Were Probably Not So Lucky).
In addition the DNC was proven to have rigged the primary in 2016. The Democratic Primary is essentially a privately held election & used this as their defense in court as to why it is okay to rig their own Primary. Unfortunately without the same types of leaks we were able to get last time in 2016, who really knows what the DNC is getting away with this time. So whomever claims, "If Bernie can't win the Primary, that is proof he also can't win the General." doesn't know what they're talking about & doesn't understand our system & the differences between the two types of elections.
Joe Biden absolutely will not energize new voters,
young voters, Independents, or Populist-Left Progressives to come out & vote (Of
Which He Needs To Win). I am a Progressive in the 18-45 age demographic
(Currently 29 Years Of Age) who has always been a registered Democrat. I would vote for Bernie
in a heartbeat, but I absolutely will not vote for Biden who has told my generation to, "Give Me A Break." referring to our economic hardship, & told his big money donors, "Nothing Would Fundamentally Change." Biden fought hard to cut Medicare, Medicaid, Social Security, & Veterans Benefits.
The American people know the corrupt status quo doesn't work for them.
The only thing that can beat a Right-Wing fake Populist (Like Trump), is
a Left-Wing real Populists (Like Bernie), the status quo (Like Joe
Biden) will always loose. Bernie beats Trump, Trump Beats Biden!