WASHINGTON — The Senate’s proposed budget blueprint stretches 93 pages, sketching out trillions of dollars in spending over the coming decade on areas ranging from the military to Medicare.

But perhaps all that really matters — and why senators are preparing to stay up late on Thursday night — is a few sentences buried deep into the document. A pair of congressional committees, it says, are to come up with “changes in laws within its jurisdiction” that would increase the deficit by not more than $1.5 trillion over a decade.

On those few cryptic words rest the success or failure of President Trump’s top legislative goal, overhauling the tax code. (Another parliamentary instruction could pave the way for opening the Arctic National Wildlife Refuge to oil drilling — another potential flash point down the line.)

The rest, even Republicans admit, is filler.

“Everything in here can be ignored, basically,” Senator David Perdue, Republican of Georgia and a member of the Budget Committee, said at a meeting of the panel this month. He described the budget process as “a fraud being perpetrated on the American people.”