Leadership conventions and leadership challenges in the Ontario New Democratic Party (previously known as the Co-operative Commonwealth Federation, Ontario Section).

Ontario CCF Leadership Convention, 1942

(Held on April 3, 1942.)

• JOLLIFFE, Edward winner
• COTTERILL, Murray

(Note: The vote totals do not appear to have been announced.)

Ontario CCF Leadership Challenge, 1946

• JOLLIFFE, Edward winner
• DUNCAN, Lewis

Ontario CCF Leadership Convention, 1953

(Held on November 21, 1953.)

First ballot:

• YOUNG, Fred 154
• MACDONALD, Donald C. 127
• BREWIN, Andrew 75

Second ballot:

• MACDONALD, Donald C. 181
• YOUNG, Fred 175

(Note: These totals are taken from an interview with Donald C. MacDonald several years after the convention. They do not appear to have been announced at the convention itself.)

Ontario NDP Leadership Convention, 1961

(Held on October 8, 1961.)

• MACDONALD, Donald C. acclaimed

Ontario NDP Leadership Challenge, 1968

(Held on November 17, 1968 in Kitchener, Ontario.)

• MACDONALD, Donald C. 859
• RENWICK, James 370

Ontario NDP Leadership Convention, 1970

(Held on October 4, 1970.)

• LEWIS, Stephen 1188
• PITMAN, Walter 642
• CAMPBELL, Douglas 21

(Note: Douglas Campbell challenged Stephen Lewis for the party's leadership in 1972, without success.)

Ontario NDP Leadership Convention, 1978

(Held on February 5, 1978.)

First ballot:

• CASSIDY, Michael 675
• DEANS, Ian 623
• BREAUGH, Michael 499

Second ballot:

• CASSIDY, Michael 980
• DEANS, Ian 809

Ontario NDP Leadership Convention, 1982

(Held on February 7, 1982.)

• RAE, Bob 1356
• JOHNSTON, Richard 512
• FOULDS, Jim 232

Ontario NDP Leadership Challenge, 1986

(Held on June 22, 1986 in Hamilton, Ontario.)

• RAE, Bob 776
• ORENSTEIN, Ian 38

Ontario NDP Leadership Convention, 1996

(Held on June 22, 1996 in Hamilton, Ontario.)

First ballot:

• HAMPTON, Howard 649
• LANKIN, Frances 611
• KORMOS, Peter 434
• SILIPO, Tony 232

Second ballot:

• HAMPTON, Howard 806
• LANKIN, Frances 691
• KORMOS, Peter 402

Third ballot:

• HAMPTON, Howard 971
• LANKIN, Frances 793

(Note: There were eighty spoiled ballots on the final count, mostly from disgruntled supporters of Kormos.)