I reckon FDR has managed to do as much as he could because he is already wealthy and doesn't have to worry much about funding election campaign. He did not have to beg to rich people and businesses for funding in exchange for doing favours for them. After all, there is strong correlation with how much campaign funds you have with thei likelihood of winning the election.

But doesn't this only prove that it was the man and not the ideology who got voted?

The man, the legend.

Let's run through the recent story so people have it:

(First on FDR, that was before 45 years of anti-communist rhetoric, which frankly turned into anti-government-policy rhetoric.)

Jimmy Carter: Told people to conserve and got voted the fuck out.

Bill Clinton: After successive losses Bill figured out "it's the economy stupid". And when you run against an incumbent (Bush senior) you have to run from the center. So that's what he did. And he won.

Gore: After the population hopefully warmed up with Bill Clinton, he stuck his head out left with climate change. And bam he lost the election. Thanks 3rd party protest voters!

Obama: So guess what Obama learned? Don't stick your head out. He ran on broad "hope", hoping the ambiguity would be enough considering Bush's disastrous wars. And he won.

Hillary Clinton: After the population hopefully warmed up with Obama, she stuck her head out just a tiny itty little bit left with the Map Room to fight climate change. And guess what happened? Bam she lost. Thanks protest non-voters!

Biden: Just like Obama learned from Gore, Biden learned from Hillary that you don't stick your head out left. And he was running against an incumbent, so once again when you do that you run center. He's actually been governing more from the left, but he ran center. 

And people are amazed that they don't run an extreme left platform? Every time they stick their head out a little itsy bitsy tiny bit left they lose. And the next guy learns to go to the center to win.

So how do you get them to move left? By giving them victories. Consistent and overwhelming victories. Because when they lose, like they've lost 20 years out of the last 24 years, they will go to the centre to find votes. You don't get big steps without the small steps.