Warren shows signs of broadening her base

Sen. Elizabeth Warren (D-Mass.) appears to be growing her share of support from black voters, who have been slow to warm to her campaign.

A new poll from NBC News and The Wall Street Journal found Warren in second place among black voters with 13 percent support, her best showing in any poll to date. That’s up from 8 percent in the previous survey from July, although the 5-point swing is within the poll’s margin of error.

An Economist–YouGov survey released Wednesday found Warren’s support among black voters at 11...