Mars definitely had the potential for life in the distant past, but due to the loss of their magnetic field, it lost its atmosphere and then the water.
If there is any microbial life there now, it'll be buried somewhere, protected from the surface temperature extremes and radiation. We may never find it.
I don't know if Mars was stable long enough while it had liquid water and atmosphere to develop complex life, much less intelligent life. It would be cool if it was though.