How are they similar in the primaries?
Both win easily states that they will loose for sure in the general election. (will loose for Hillary, lost for Romney)
So, the most loyal electorate of their parties for both candidates is the one which is useless in the general election.
Not sure I agree fully, at least with regard to Clinton. Clinton won the MA primary and will probably win NY and IL, three safe Dem states in the general with a lot of EVs. Add in VA and MD and CA. Plus Clinton is hugely popular in the Black community, another safe Dem constituency (albeit one that is dispersed around the country).
