He won as the underdog in the 1968 presidential election , winning 65.6 % of the vote on a 92.2 % voter turnout running against Gunnar Thoroddsen . Starting as the underdog in the 1968 presidential election , running against ambassador Gunnar Thoroddsen who initially had a 70 % lead in the opinion polls , EldjÃ rn won 65.6 % of the vote on a 92.2 % voter turnout .