Dark-horse
candidate
Dead
as a doornail
Dead
duck
Dime
a dozen
Do
or die
Dog
days of summer
Dog-eat-dog
world
Dog's
life
Don't
count your chickens before they hatch
Don't
look a gift horse in the mouth
Don't
take any wooden Nickels
Dot
your i's and cross your t's
Down
in the dumps
Down
the drain
Down
the hatch
Down-to-earth
Down-to-the-wire
Draw
the line at
Dressed
to the nines
Drive
a hard bargain
Drive
you crazy
Drop
in the bucket
Drop
you like a hot potato
Dull
as dishwater
Dutch
treat
Dyed-in-the-wool