user: Question: How many were first elected when the incumbent was Morgan M. Moulder?
Columns: ['District', 'Incumbent', 'Party', 'First elected', 'Result', 'Candidates']
Types: ['text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['Missouri 1', 'Clare Magee', 'Democratic', 1948.0, 'Re-elected', 'Clare Magee (D) 54.4% Samuel W. Arnold (R) 45.6%']
SQL:

assistant: SELECT COUNT("First elected") FROM "Table" WHERE "Incumbent" = 'Morgan M. Moulder';