House and Senate farm bill leaders are to meet again Wednesday in what’s become a political rollercoaster that risks tossing Congress into a flood of overpriced milk come Jan. 1.

Just last week, the Agriculture Committees were predicting agreement soon on how to rewrite the commodity title and replace the current system of direct cash payments to producers. But Tuesday’s tone was much more skeptical, and House Ag Chairman Frank Lucas (R-Okla.) warned his party it had to be prepared “for how consumers will react at the grocery store when a gallon of milk doubles.”

“I was a very hopeful fellow a few days ago. I’m becoming pessimistic,” Lucas told POLITICO after a meeting of House committee chairs in the Capitol. “I’m trying to explain to everybody what the consequences are. I’m going to push to the last moment, but I would acknowledge to you that if we can’t make progress, something has to happen.”

Indeed, absent some agreement, dairy policy will revert next month to a 1949 law that prescribes a post-World War II vision of a more muscular government buying up dairy products directly to boost prices. The Agriculture Department would pay producers $38.54 per hundredweight compared to a market now running near $16.22. The result would be havoc — and many estimate a doubling in consumer prices for milk.

At this stage, few expect a farm bill can be written and enacted before Jan. 1, but the hope has been to reach enough of a consensus that the committees can be confident of producing a five-year plan as part of a budget deal between the White House and Speaker John Boehner (R-Ohio).