Obama doesn't have to. He understands the Republican leadership enough to know saying he will veto is as good as already having vetoed.
Republicans will now start saying we don't have 66 votes, we have to find common ground, reach across the aisle, party of yes, yada yada yada.
They give up before they try instead of following through anyway and letting the process play out. One never knows for sure what might happen, we only know for sure that Republicans are afraid to try.
-PJ
“Republicans will now start saying we don’t have 66 votes, we have to find common ground, reach across the aisle, party of yes, yada yada”
This is not the fight, we will get him on the (fill next fight in here).