Ostensibly, the Democrats' platform has a lot to appeal to a broad coalition of large and growing groups in the US: Women, minorities, the disabled, city dwellers, the elderly, the young, parents, the working and middle class. If this coalition could gel and be got to the polls every election, the Dems would be unstoppable. Instead, they're barely holding on against a Republican party whose platform (to the extent they have one) should be a visceral threat to those groups. It seems like the Dems are at a permanent disadvantage in American electoral politics, having to be twice as good to get half as far.

Is this a matter of policy misalignment? Are D and R voters constitutionally different, and hold their parties to different types of expectations? Is it a problem of ineffective communication? To what degree is it a function of the quirks of US election law and tradition? Is it due to a reluctance to get down in the mud with the opposition?

To what degree is there a consensus diagnosis of the problem(s)? What, if anything, are they trying to do about it?