Voltage divider value float when not connected

I have a voltage divider setup going into A4. 12v is the input. R1 is a 20k resisted and R2 is a 10K. When the output voltage divider wire is connected, i get a good constant reading... but when I disconnect the the wire... the reading floats... I thought the 10k resistor would act like a pull-down. Any info would help. Thanks in advance.

The other end of the 12V is still acting like an antenna tho, 5/6 10/22 of any signal it picks up appears at the analog input, which needs <1uA to change its level.