MARGINAL

(POLITICS) [noun] [C], [adjective] [UK and ANZ] - (a political area or parliamentary position) which can be won by only a small number of votes because support for the main political parties is equally divided among the people votingLabour lost two of the key marginals in London.The minister's own seat is a Tory marginal.The marginal Tory constituency was held by 2 200 votes in 1992.This is the most marginal seat in the country which the Liberal Democrats won by only seven votes.