How many incumbents are there in the georgia 8 district when the party is democratic?
{'header': ['District', 'Incumbent', 'Party', 'First elected', 'Result', 'Candidates'], 'page_title': 'United States House of Representatives elections, 2010', 'section_title': 'Georgia', 'caption': 'Georgia', 'rows': [['Georgia 1', 'Jack Kingston', 'Republican', '1992', 'Re-elected', 'Jack Kingston (R) 71.6% Oscar Harris (D) 28.4%'], ['Georgia 2', 'Sanford Bishop', 'Democratic', '1992', 'Re-elected', 'Sanford Bishop (D) 51.4% Mike Keown (R) 48.6%'], ['Georgia 4', 'Hank Johnson', 'Democratic', '2006', 'Re-elected', 'Hank Johnson (D) 74.7% Liz Carter (R) 25.3%'], ['Georgia 5', 'John Lewis', 'Democratic', '1986', 'Re-elected', 'John Lewis (D) 73.7% Fenn Little (R) 26.3%'], ['Georgia 6', 'Tom Price', 'Republican', '2004', 'Re-elected', 'Tom Price (R) unopposed'], ['Georgia 7', 'John Linder', 'Republican', '1992', 'Retired Republican hold', 'Rob Woodall (R) 67.1% Doug Heckman (D) 32.9%'], ['Georgia 8', 'Jim Marshall', 'Democratic', '2002', 'Lost re-election Republican gain', 'Austin Scott (R) 52.7% Jim Marshall (D) 47.3%'], ['Georgia 9', 'Tom Graves', 'Republican', '2010', 'Re-elected', 'Tom Graves (R) unopposed'], ['Georgia 10', 'Paul Broun', 'Republican', '2007', 'Re-elected', 'Paul Broun (R) 67.4% Russell Edwards (D) 32.6%'], ['Georgia 11', 'Phil Gingrey', 'Republican', '2002', 'Re-elected', 'Phil Gingrey (R) unopposed'], ['Georgia 12', 'John Barrow', 'Democratic', '2004', 'Re-elected', 'John Barrow (D) 56.6% Raymond McKinney (R) 43.4%']]}