That matters because it was Paul, R-Ky., who last month single-handedly prevented Congress from speedily moving ahead on a sweeping budget deal, triggering a short government shutdown as he protested his own Republican Party's deficit spending.
This time, Paul hasn't yet decided on whether he'll seek to slow the measure, but he's clearly unhappy with the closed door talks, telling McClatchy in an interview this is a "rotten, terrible, no good way to run your government."
In two conversations with McClatchy, Paul said he'd make up his mind after he sees the $1.3 trillion spending plan, which Republican leaders had hoped to produce last week but were working round the clock with Democrats to finish Wednesday. Details are expected to be finalized later in the day.
"You have to know what's in it," Paul said. "Really, should we be looking at 1,000 page bills with 24 hours to decide what's in them? It's really not a good way to run your government."