Interior minister of North-Rhine Westphalia Ralf Jäger | Federico Gambarini/AFP/Getty Images German investigation of Berlin terror attack becomes political football Placing blame in a year of elections.

BERLIN — Party politics are creeping into the investigation of the Berlin Christmas market terrorist attack.

Back from their winter break, members of Germany's lower house of parliament, the Bundestag, are set to debate how Anis Amri, the 24-year-old suspect, could have evaded the country's security system, even though he was listed as radicalized and had been monitored by security forces for months.

The discussion, which involves questions of government responsibility and authority over the security services, is sure to become a game of political football, especially in advance of regional and national elections, pitting the government's coalition partners against each other.

While officials from Merkel’s Christian Democrats (CDU) say the Bundestag should form an investigative committee across party lines, their coalition partner, the Social Democrats (SPD), prefers an external special envoy.

What might seem at first blush a discussion about the most effective way to investigate the attack is also a case of political tactics ahead of a key upcoming regional election in the state of North Rhine-Westphalia, Bundestag officials said.

"It's all about NRW," said an SPD parliament official, using an acronym for the state and speaking on condition of anonymity.

Germany’s most populous state is scheduled to elect a new regional parliament in May — and the result is widely seen as an important indicator of what to expect in September's national election.

Currently governed by an SPD-Green party coalition, North Rhine-Westphalia is also the state where Amri first registered as a refugee in Germany. And since the terrorist attack in mid-December, more and more flaws in the regional authorities' monitoring of Amri have been revealed.

According to unconfirmed German media reports, for example, Tunisian and Moroccan security officials warned the state's criminal investigator’s office three times that Amri was planning an attack, most recently just two months before the Christmas market massacre.

Despite those reports — and growing public criticism — the SPD’s state premier Hannelore Kraft continues to back her interior minister Ralf Jäger, a member of the SPD, who officially oversees the agencies.

"My answer to your question is a clear Yes," Kraft told journalists last week when asked if Jäger still had her full support.

According to Bundestag officials, many in the SPD fear that a political committee might uncover information to back up those claims, which, in turn, would weaken Kraft, their top candidate, in her campaign for reelection.

Accordingly, the SPD's push to first appoint an external special envoy is widely understood as an attempt to buy time ahead of the state election, since that person likely won't be granted as much access as MPs on a committee. In addition, if an investigative committee starts its work later this year — an idea the SPD doesn’t oppose per se — it will likely not release its results before the regional election in May.

Volker Kauder, who chairs Merkel's conservative bloc in the parliament, and the SPD’s parliamentary group chair Thomas Opperman, as well as Gerda Hasselfeldt, who leads the parliamentary group of the CDU’s Bavarian sister party the Christian Social Union, are expected to meet to discuss both options Tuesday.

Either way, neither an investigative committee nor a special envoy will be the only one in the parliament looking into the case.

On Monday night, the Bundestag's Parliamentary Control Panel, a permanent committee in charge of controlling the country's intelligence services, announced plans to set up its own special task force, as well.