ISTANBUL, Dec 14 (Reuters) - A Turkish court on Wednesday sentenced Istanbul Mayor Ekrem Imamoglu, a popular rival of President Tayyip Erdogan, to more than two years in prison and imposed a political ban for insulting public officials, in a ruling set to go to an appeal.The ruling comes just six months ahead of scheduled presidential and parliamentary elections, in which Imamoglu has been mooted as a potential strong challenger to Erdogan.Imamoglu, from the opposition Republican People's Party (CHP), was tried over a speech after 2019 local elections in Istanbul when he said those who annulled the vote were "fools."Imamoglu narrowly won the municipal election in March 2019, beating a candidate from Erdogan's ruling AK Party.The outcome of the 2023 election is seen hinging on the ability of the CHP and others in opposition to join forces around a single candidate to challenge Erdogan and the AKP, which has governed Turkey for two decades."