The two most interesting questions in US politics at the moment are whether Ms Elizabeth Warren will be the Democratic candidate in 2020 and whether President Donald Trump will still be around to duke it out with her.

Neither is certain, of course, but Ms Warren's ascendance already guarantees that the 2020 election will come down, as elections often do, to a fight between old and new. Or, in this case, between unbridled economic markets and a new, more regulated framework for capitalism.