If the POTUS thinks a bill is unconstitutional, he is under obligation not to sign it--not pass the buck to the SCOTUS.
The philosphy of the balance of powers is the key thing to keep in mind here. All three branches are responsible to defend the Constitution. The SCOTUS is actually the last line of defense.
We need to quit playing games and patting ourselves on the back for it. It is precisely how we have gotten into the mess we are in as a nation.