Michael Hiltzik: Billionaires emerge as the defining campaign issue for 2020

With the 2020 presidential campaign in full swing, it is clear that the defining issue of the election will be economic inequality - and that puts America's billionaires in the dock.

Proposals for a tax on extreme wealth have been put on the table by Democratic candidates Elizabeth Warren and Bernie Sanders, eliciting responses of varying vehemence from the billionaires lobby.

These responses, as we've reported, have been mostly negative, although here and there a few billionaires have allowed that, yes, they may have too much money and it might be good public policy to redistribute some of it through taxation.

The wealth tax proposals are part of a general attack on economic inequality that all the Democratic candidates share, to some extent.

"The middle class is getting killed," former Vice President Joe Biden said during the Dec. 19 Democratic debate. "The middle class is getting crushed. And the working class has no way up as a consequence of that ... . The idea that we're growing - we're not growing. The wealthy, very wealthy, are growing. Ordinary people are not growing. They are not happy with where they are."

Even the two certified billionaires in the Democratic race have expressed support for raising taxes on the ultra-wealthy. "I've been for a