The phrase "slender margin" means a very small or narrow difference or gap between two things.
Sentences with «slender margin»
It was their tendency during qualifying to win by slender margins but win they did and Italy amassed a very healthy 24 points from qualification. (footballticketpad.com)
OTOH, elections in the US today are won on slender margins. (realclimate.org)
Having achieved a renewed mandate — albeit by a slender margin in the popular vote — and with the devastation wrought by hurricane Sandy fresh in the memory, Obama may be well placed to seize the moment. (newscientist.com)