user: Question: Which Source has a Undecided of 2%?
Columns: ['Source', 'Date', 'Clinton', 'Obama', 'Undecided']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['SurveyUSA', 'May 16–May 18, 2008', '42%', '55%', '1%']
SQL:

assistant: SELECT "Source" FROM "Table" WHERE "Undecided" = '2%';