Kevin McCarthy even vowed to block House consideration of bills sponsored by GOP senators who voted for it.
But a slew of GOP senators voted for it anyway, including 4 who are retiring and 14 who will remain.
"Kevin's in a tough spot," Republican Sen. Kevin Cramer of North Dakota, a former House Republican and an opponent of the omnibus himself, told CNN's Manu Raju.
"Statements like that... is the very reason that some Senate Republicans feel they probably should spare them from the burden of having to govern."
Additionally, four Republican senators who voted for the bill are retiring, making the threat meaningless to them.