This could be a momentous week for Germany's future. Both chambers of parliament must vote on a constitutional amendment that will ease the country's debt brake, opening the way for a huge spending package for armaments, infrastructure, and climate protection agreed by the center-right bloc of  Christian Democratic Union (CDU) and Christian Social Union (CSU) and the center-left Social Democratic Party (SPD) — who are negotiating to form a new government — as well as the Greens.

The amendment passed the Bundestag, on Tuesday, March 18 with the necessary two-thirds majority — now it will be up to the second chamber of the German parliament, the Bundesrat, which is due to vote this Friday. Here too, at least two-thirds of members must vote for the amendment for it to pass. But this is not a sure thing, as some regional parties have voiced objections.

The Bundesrat represents Germany's 16 state governments, which dispatch a handful of representatives each, most often leading ministers in the state's Cabinet.

Located in Berlin, the Bundesrat has the right to accept or reject any bills that affect the states — which this new amendment will do, as it also allows the states to loosen their own debt brakes.

The Bundesrat's 69 seats are distributed among the states, though not neccessarily propotionally in terms of population: For example, Germany's most populous state, North Rhine-Westphalia, with 18 million inhabitants, has six Bundesrat votes — but so does Lower Saxony, which only has 8 million inhabitants.

Similarly, the states with the smallest populations — Bremen and Saarland (both under a million inhabitants) — have three votes each, but so does Hamburg, which has 1.9 million inhabitants.

Each state's seats are divided among the parties according to their relative strength in the coalition government: Bavaria, for example, has six Bundesrat seats, four of which are occupied by the conservative Christian Social Union (CSU), and two by their junior coalition partners, the Free Voters (FW).

But — and this could prove a sticking point this week — each state government must vote in a single bloc in the Bundesrat, regardless of party affiliation. If Bavaria's two FW representatives vote a different way to their CSU colleagues on Friday, all six votes will be considered invalid.

The margins are tight: The debt brake amendment needs at least 46 of 69 votes to pass the Bundesrat, and the state governments exclusively run by the CDU, SPD and Greens make up only 41, so Bavaria's six votes could be crucial. In other words, the FW, a tiny party nationally, theoretically has the power to scupper the entire undertaking.

This was indeed the scenario that threatened to unfold last week, when FW leader and Bavarian Economy Minister Hubert Aiwanger said after a special meeting of his party in the Bavarian parliament, "We cannot agree to this paper as it currently stands, because we see more danger than opportunity for the stability of our country." But, perhaps because this move would cost the FW participation in the current Bavarian government, his party has since withdrawn its objections, and agreed to vote for the amendment.

Aiwanger's objection was that lifting the debt brake would encourage too much government spending, but other Bundesrat members have voiced different concerns.

Bremen Economy Minister Kristina Vogt, of the socialist Left Party, which is in coalition in the city-state with the SPD and the Greens, demanded that more of the planned infrastructure package be allocated to the states, rather than left to the federal government. She too threatened to vote against the package, which would mean Bremen's votes would also be invalid.

There is a similar situation in the eastern state of Mecklenburg Western-Pomerania, governed by a coalition of SPD and the Left Party. Here too, the Left Party has expressed misgivings about the massive increase in military spending. Meanwhile, the Sahra Wagenknecht Alliance (BSW), also vehemently against increased military spending, is currently in government in two other eastern German states. Equally, the Free Democratic Party (FDP), self-styled guardians of Germany's debt brake, is in government in Rhineland-Palatinate and Saxony-Anhalt.

It is not unusual for the Bundestag and the Bundesrat to disagree. "On the contrary, especially in difficult times it often happens that the Bundesrat says no," said Christoph Gusy, professor of constitutional law at Bielefeld University. "That isn't a constitutional crisis, that's a very normal situation." In such cases, bills are returned to the Bundestag, where they have to be renegotiated.

What is unusual, however, is when states invalidate all their Bundesrat votes by splitting them. According to Gusy, such a situation has only arisen twice before — and one of those times it appeared to be the result of a misunderstanding. The other case was in 2002, when the Brandenburg government, an SPD-CDU coalition, split its votes between yes and no on a proposed immigration bill. The confusion caused uproar in the chamber, and in a subsequent court case, the Constitutional Court ruled that Brandenburg's votes were invalid.

If the Bundesrat were to vote against the debt brake amendment on Friday, it would set off "a severe political crisis" said Gusy. 

It would certainly be a major blow to the authority of the presumptive next German chancellor, Friedrich Merz, leader of the CDU, who is currently in coalition talks with the SPD. "The forming of this new government is to some extent built on this new debt package," Gusy said.

Merz's future government is very much counting on being able to spend that money — should the Bundesrat say no on Friday, the bill goes back to a brand new Bundestag next week — when a two-thirds majority will not be guaranteed. Then, all bets will be off.

Edited by Rina Goldenberg