President Joe Biden’s departure from the principle of “parity” in his first budget request — or equal increases in defense and nondefense discretionary spending — signals a rocky road ahead for next year’s appropriations bills.

Biden ended up blessing slightly more than a 1.5 percent increase for the Pentagon in the budget outline the White House will unveil later on Friday, while domestic and foreign aid agencies on average would see larger boosts, a source who spoke on condition of anonymity confirmed.

That’s unlikely to sit well with Republicans, while it’s not even a safe bet that Democrats will be fully on board with such a slim increase for defense that doesn’t keep pace with inflation. Leading progressives in both chambers over the last year have called for up to 10 percent cuts in the Pentagon budget.

That prospect could spell trouble for the fiscal 2022 budget resolution Democrats want to adopt to pass filibuster-proof reconciliation bills implementing Biden’s ambitious infrastructure and other spending plans.

It’s even more problematic for fiscal 2022 appropriations, since there’s little chance Republicans in the 50-50 Senate will go along with Appropriations subcommittee allocations, known as 302(b)s, that endorse a big increase for nondefense and a skimpier defense figure. Unlike reconciliation bills, which only require a simple majority, it still takes 60 votes to advance appropriations bills in the Senate.

Parity as a principle in discretionary spending arose as successive Congresses negotiated budget deals that raised the defense and nondefense spending caps from the 2011 deficit reduction law more or less equally. Republicans are already signaling they won’t support insufficient defense funding or a disproportionate increase in nondefense.

“China and Russia are building up their militaries,” Senate Appropriations ranking member Richard C. Shelby, R-Ala., said in a statement. “Shortchanging ours would signal weakness to them. We need parity to keep America strong at home and abroad.”

Rep. Tom Cole, the top Republican on the Labor-HHS-Education Appropriations Subcommittee, echoed Shelby, saying “any increases to nondefense discretionary spending, even those with bipartisan agreement, must not be delivered at the expense of our dedicated service members.”

Cole, R-Okla., said Congress “has no greater responsibility than to provide our military with the training and resources needed to confront the security challenges and threats presented by an ever-changing world.”

An added challenge is posed by the expiration of the discretionary spending caps at the end of the current fiscal year. Under the cap regime, Democratic and Republican lawmakers were bound by the law not to appropriate above the caps. The only way to exceed the caps was to negotiate a budget deal. With the caps gone, Congress goes without an existing budget framework.

Flat funding, no earmarks?

So if the House and Senate fiscal 2022 budget resolutions and appropriations bills reflect a departure from parity, odds are Congress will not reach agreement on individual appropriations bills. That could lead to a full-year stopgap that extends spending at roughly fiscal 2021 levels.

And it could avoid a messy intraparty squabble among Senate Republicans over earmarks, which House Democrats and Republicans have agreed to bring back this year after a decadelong absence.

Senate Appropriations Chairman Patrick J. Leahy, D-Vt., wants to do the same, and says he’ll go forward even without GOP support if necessary. Top Republican appropriators would like to go along, but as recently as two years ago more than half the Senate GOP Conference voted to permanently ban earmarking on their side.

A continuing resolution simply flat-funds federal agencies for its duration, so while defense accounts would have to do without their small boost, nondefense programs would also be frozen — an outcome many Republicans might endorse. And no earmarks would be allowed in a CR, depriving Democrats of such prizes to tout back home and keeping the internal Senate GOP debate from spilling into the open.

It may be difficult to even bring up spending bills in the Senate under the topline figures Biden has outlined. Unlike in the tightly controlled House, where Speaker Nancy Pelosi, D-Calif., just needs a bare majority to pass bills, the evenly divided Senate has fewer procedural options.

Unlike a piece of legislation or an executive branch nominee, Democratic leaders can’t discharge the 302(b) allocations from the Appropriations Committee by a majority vote on the floor if that panel deadlocks on a tie vote.

So if Republicans stick together in opposing the spending framework, they can prevent ratification of the allocations. That doesn’t necessarily mean Democrats couldn’t then mark up and attempt to bring spending bills to the Senate floor, but getting 60 votes would appear out of reach.

Even without the specter of a fight over defense spending, it is hard to see a smooth path to agreement on appropriations bills. Some point to the fact that Democrats just passed a $1.9 trillion pandemic aid package with zero GOP support, on top of trillions more in un-offset domestic spending last year, as sapping Republicans’ appetite for a bipartisan appropriations deal.

“Given no statutory spending caps, partisan budget resolutions, and trillions of mandatory spending already having been spent in discretionary accounts, I would be stone cold shocked if we have any cooperation on appropriations bills,” a former Senate GOP budget aide said.

It’s still possible that even with no agreement on spending limits and individual appropriations bills, the two parties could negotiate a spending agreement at the end of the year with toplines that both sides of the aisle can live with.

“Sooner or later there’s going to have to be a deal and Republicans are going to have to be at the table on discretionary,” said Tom Kahn, a former House Budget Committee Democratic staff director.

Kahn expects there will at least be an attempt to reach a bipartisan agreement on what could be an omnibus at the end of the year. “Before this thing gets signed into law, at some point or another there will be a negotiation between the House and the Senate and the White House,” he said.