RMT members began 48 hours of action at midnight on Saturday after talks with management over planned redundancies for conductors on the service broke down midweek.
The union said the 9-1 vote for strikes on a 50 per cent turnout would leave politicians "dancing in the streets" in their own elections.
But Tories on the Greater London Authority bemoaned the fact that "only" 43 per cent of all staff balloted had voted Yes.
Transport spokesman Richard Tracey blustered that it was "absurd" that passengers could face disruption because "43 per cent of train guards - a mere 53 workers - have opted for strike action."
He ominously suggested that transport bosses and Mayor Boris Johnson "need to begin to think differently" on how to prevent strikes.
GLA Tories have previously said strike votes should only be valid if over 50 per cent of those balloted support action, even though only 38 per cent of Londoners turned out for the 2012 assembly elections.
RMT general secretary Bob Crow accused those calling for a threshold of rank hypocrisy.
He said the mayor and Tory "clowns" on the GLA would have to step down if they applied the same rules to themselves as they wanted to force on the unions.
"This policy on one form of democracy for the political class and another for the working class has the whiff of the military junta about it."
The average turnout for police commissioner elections was less than 15 per cent, while for the the 2009 Euro elections it stood at 34.9 per cent.
And a mere 36.1 per cent of the electorate voted Tory at the 2010 general election.