Republicans love smoke-and-mirrors budgeting. They're laying off thousands of workers chaotically even though salary costs are a tiny fraction of the federal budget. Elon Musk is pretending to save far more money than he really is. Now Senate Republicans are trying to hide the cost of extending the 2017 tax cuts using a new wheeze called the "current policy baseline."
This one is a pistol, but it's a little trickier than the others. Take a look at the chart below:

The cost of the 2017 tax bill has so far averaged a little over $200 billion per year (blue bars). So let's just take that as the new zero! If we do, the apparent cost of extending the tax cut goes down from $3.6 trillion to $1.8 trillion. That certainly makes things easier on everyone.
It's not real, of course. Suppose you're paying off $500 per month on your car. After five years it's done and you decide to buy a new car with the same payments. If you assume that $500 is your "baseline" then the new car costs nothing. It's an exciting thought.
But it ain't true. Call it anything you like, but that car is costing you $500 per month in actual money. If you don't account for that in your household budget you're going to be screwed pretty quickly.
It's the same for extending the 2017 tax bill. Whether you like it or not, it's going to cost about $3.6 trillion and it's going to swell the national debt by $3.6 trillion.
But Republicans don't want it to increase the national debt by $3.6 trillion. They're against debt, you see. But they're also deeply in favor of tax cuts for the rich. What to do?
Pretend and extend, my friends. Can they get away with it under Senate rules? Probably not, but it's worth a try. Stay tuned.