Itnow looks as if there will be a by election in Glasgow North East. Mr Martin's official spokesperson has just said that he will stand down as an MP too.
Here are the results from the 2005 General Election when Mr Martin stood as an independent. Where will the left vote go in a by election?
Speaker Michael Martin 15,153 53.3%
Scottish National Party John McLaughlin 5,019 17.7%
Socialist Labour Doris Kelly 4,036 14.2%
Scottish Socialist Graham Campbell 1,402 4.9%
Scottish Unionist Daniel Houston 1,266 4.5%
British National Scott McLean 920 3.2%
Independent Joe Chambers 622 2.2%
Majority 10,134 35.7
Turnout 28,418 45.8 +1.9 Speaker hold Swing -6.6