The Democratic Party is a “wide tent” party, unlike the Republicans, but being a “wide tent” creates its own issues, particularly when we have a 50-50 Senate.
On the Left we have Bernie Sanders, who is really a Socialist more than a Democrat, and does not work well with others.
Any thought that Sanders might have been President would have been a nightmare, as he does not understand Compromise.
But then, on the Right, we have Joe Manchin, who is a Democrat, but more like a Republican, and makes life difficult for Democrats, but the alternative if he joined the Republican Party or was defeated by a Republican in West Virginia, would be worse.
So Joe Biden has to do a balancing act to gain the backing of both Sanders and Manchin, and that is extremely difficult, but important, in order to accomplish the goals of his Presidency!