SELECT "Democratic" FROM table_29237 WHERE "Registered voters" = '67.8%'
what is the percentage of democratic voters in which the registered voters is 67.8%?
CREATE TABLE table_29237 (
    "City" text,
    "Population" real,
    "Registered voters" text,
    "Democratic" text,
    "Republican" text,
    "D\u2013R spread" text,
    "Other" text,
    "No party preference" text
)