Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_204_639 ( id number, "poll company" text, "source" text, "publication date" text, "psuv" number, "opposition" number, "undecided" number )

### Question ###
how many total opposition votes were cast after august 2010 ?

### Accurate SQL ###

SELECT SUM("opposition") FROM table_204_639 WHERE "publication date" > (SELECT "publication date" FROM table_204_639 WHERE "publication date" = 'august 2010')