The CDU has traditionally been the main center-right party across Germany, but it shifted toward the center under Chancellor Angela Merkel. The party remains more fiscally and socially conservative compared to parties on the left. It supports membership of the EU and NATO, budgetary discipline at home and abroad and generally likes the status quo. It is the largest party in the Bundestag.

The CSU is the sister party of the CDU in Bavaria and the two act symbiotically at the national level (CDU/CSU). Despite their similarities, the CSU is generally more conservative than the CDU on social issues. The CSU leader and premier of Bavaria, Markus Söder, ordered crosses in every state building in 2018.

The SPD is Germany's oldest political party and the main center-left rival of the CDU/CSU. It shares the CDU/CSU support for the EU and NATO, but it takes a more progressive stance on social issues and welfare policies. It is currently in a coalition government with the CDU/CSU and is trying to win back support under interim leaders Thorsten Schäfer-Gümbel, Manuela Schwesig and Malu Dreyer.

The new kid on the block is the largest opposition party in the Bundestag. The far-right party was founded in 2013 and entered the Bundestag for the first time in 2017 under the stewardship of Alice Weidel and Alexander Gauland. It is largely united by opposition to Merkel's immigration policy, euroscepticism, and belief in the alleged dangers posed by Germany's Muslim population.

The FDP has traditionally been the kingmaker of German politics. Although it has never received more than 15 percent of the vote, it has formed multiple coalition governments with both the CDU/CSU and SPD. The FDP, today led by Christian Lindner, supports less government spending and lower taxes, but takes a progressive stance on social issues such as gay marriage or religion.

The Greens, led today by Annalena Baerbock and Robert Habeck, emerged from the environmental movement in the 1980s. Unsuprisingly, it supports efforts to fight climate change and protect the environment. It is also progressive on social issues. But strong divisions have occasionally emerged on other topics. The party famously split in the late 1990s over whether to use military force in Kosovo.

The Left, led by Katja Kipping and Bernd Riexinger, is the most left-wing party in the Bundestag. It supports major redistribution of wealth at home and a pacifist stance abroad, including withdrawing Germany from NATO. It emerged from the successor party to the Socialist Unity Party (SED) that ruled communist East Germany until 1989. Today, it still enjoys most of its support in eastern Germany.

The SPD appeared to have struck gold when it nominated Martin Schulz, the former president of the European Parliament, to challenge Angela Merkel for chancellor in the 2017 elections. In what came to be dubbed as the "Schulz effect," the SPD's shake-up at the top saw the party surge in the opinion polls to up to 33 percent, neck-and-neck with Merkel's conservatives.

By May, however, the Schulz effect had faded. If the SPD wanted to prove it was a serious contender for September's federal election, it needed to retain its place at the helm of two key state governments. The first state election in Schleswig-Holstein, however, saw the CDU record an "easy" victory, winning by five points. The CDU went on to form a coalition with the Greens and Free Democrats.

Things went from bad to worse a week later, when Merkel's party defeated the SPD in their stronghold in North Rhine-Westphalia. The SPD had ruled NRW for 46 of the past 51 years. However, it only picked up 31 percent of the vote this time, seven points lower than in 2012. Schulz described the defeat as "crushing," while outgoing state premier Hannelore Kraft resigned as state SPD party chief.

Come September, with the federal election just weeks away, some pundits still gave Schulz half a chance of clinching the chancellery. However, the televised election debate between the two candidates exposed the effects of a grand coaltion. The two leaders seemed happy to agree with the other's proposals, rather than have a debate. And yet viewers still saw Merkel as the more credible candidate.

In its worst election showing since World War II, the SPD scraped just over 20 percent of the vote. It would claim just 40 seats in the Bundestag, 40 fewer than before. Schulz, however, vowed to stay on and lead the party in opposition. The move was widely welcomed by the party's rank and file. It was time for a much-needed recharge and reappraisal.

After talks to form a coalition with the Greens and FDP collapsed in November, Merkel had no choice but to turn to Schulz to form a governing coalition. After much "umming" and "ahing," the SPD leadership decided to enter preliminary talks with the conservatives. Well aware that the move would be unpopular with many in the party, Schulz said the party's 460,000 would get the final say.

However, no sooner had Schulz agreed on a preliminary deal then senior figures in SPD demanded an extensive overhaul. Schulz's failure to prevent a migration cap, establish a "citizens' insurance" scheme and abolish fixed employee contracts raised serious doubts whether party officials would agree to proceed to formal talks.

Ahead of a party conference that would see SPD members vote on the preliminary coalition plan, the movement against another grand coalition began to gather heavy steam. The face of this grassroots revolt was SPD youth wing head Kevin Kühnert. In a series of impassioned speeches, the 28-year-old didn't just win the backing of youngsters, but convinced several senior figures as well.

Despite the heavy backlash, SPD delegates still approved the coalition deal. Of the votes, 362 were in favor of talks compared with 279 against. In a bid to shore up support, then-party leader Schulz said there would be "tough negotiations" with Merkel's conservatives. But that didn't stop critics from accusing Schulz of making concessions to Merkel.

After the announcement of a coalition agreement, media reports claimed that the finance ministry had been given to the SPD, marking what some consider a major victory for the center-left party. The SPD's Olaf Scholz, the popular mayor of Hamburg, was reportedly tapped to head the ministry. If it proves true, it will be the first time in almost nine years that the SPD controls it.

In early February, tensions inside the SPD reached a fever-pitch. Gabriel told German media that Schulz didn't appreciate the job he had done as foreign minister. Days before, Schulz had signaled his desire to lead the foreign ministry. "The only thing left is remorse over how disrespectful we've become with one another in our dealings and how little someone's word still country," Gabriel said.

Former Labor Minister Andrea Nahles is a strong contender to head the center-left party. She made a name for herself as the leader of the SPD's youth branch. However, her impassioned defense of joining a Merkel-led coalition in January was seen as the key to clinching a majority to move forward on formal talks. But she'll have to wait until April 22, when the SPD will choose its next leader.

If anything, the decision to pursue a Merkel-lead coalition has further dragged support for the party. A poll published in February showed the party at 16 percent if elections were held on February 18, a 2-percent drop from the previous poll a month before. Polls now show the SPD neck-and-neck with the far-right AFD.

SPD members – all 463,723 of them – will now vote on whether the party can join a coalition with the CDU and CSU. The members have until March 2 to submit their ballots with results expected shortly after the due date. Until then, Germany waits on the prospect of a new government.