Why does Biden claim he has "the most progressive record of anyone running"?

[Otto Lidenbrock]

28. Biden's candidacy is a tale of generational changes

When Biden was elected for the first time in the early 1970s it was still common for democrats to walk back on how liberal they were in order to gain the trust of an older, more conservative vote.

The usual thing to say was support the civil rights movement and be liberal on equal opportunity, but fiscally conservative regarding social programs and the extent of government outreach.

Those old voters a young Biden courted are now long deceased. Biden himself is now at the age of those people in the 1970s and now generally America has become more liberal, young Americans and young voters are more engaged at all levels, and the Democratic Party grassroots is no longer interested in bending to a whim of bipartisanship when the other side can go to the extremes at their will.

A young Biden was trying to tell old people he was not too liberal. An old Biden is trying to tell young people he is very liberal.

A young Biden didn't have a record to point to so he had an advantage of being taken by his word. An old Biden has a long record so he has a disadvantage of it being dissected to the nth degree.

I am interested to see how he handles this.