Polls indicated that Merkel's party is likely to win but fall well short of the parliamentary majority needed to form a government. The CDU is now hoping to form a coalition with its traditional ally, the Free Democratic Party (FDP). That result is too close to call.
The SPD's fortunes have been rising recently amid growing nervousness over Merkel's plans to reform the economy. Just a few weeks ago it looked as if Schroeder would be swept from office. Now, the polls say a left-leaning coalition, linking the SPD, the Greens and a new far-left party, is a possibility. Some even say Schroeder could try to convince the Free Democrats to switch to his side.
Merkel has tried to focus voters on Germany's economic stagnation the past several years. The German economy is Europe's largest, yet it has barely grown in five years. Unemployment is hovering at or near a record high.
"Well, Mr. Schroeder is walking through the country and saying that the seven years of [his ruling coalition] were seven good years for Germany, and I have to say honestly that in the ears of many, many people this is really utter nonsense," Merkel said.
Schroeder acknowledged Germany's economic problems, but said he's launched a package of economic and labor reforms that will stimulate the economy.
"I'm not saying [this economic stagnation] is something that I find satisfactory," Schroeder said. "How would I come to that idea? But it is evident that the reforms which we have launched -- which no one had the courage to do until now -- are starting to take effect. That is exactly why [these reforms have to be continued.]"
Schroeder said Germany's economic problems began with his predecessor, Helmut Kohl, the former leader of Merkel's CDU. Kohl, in the 1990s, passed massive packages of aid for the former East Germany. The result was a short-term boom, followed by a longer-term bust.
Merkel puts the blame more squarely on Germany's high tax rates and generous labor and health benefits. These have made companies reluctant to hire new workers and have forced some to move production and employment to lower-cost countries.
The reform packages outlined by both the CDU and SPD are broadly similar -- and some polls even suggest a "grand coalition" between the two might be possible. Such a coalition, however, would not likely include Schroeder.
The vote could have strong implications for the country's foreign policy, particularly its position vis-a-vis Turkey's hopes to join the European Union and Germany's strained relations with the United States.
Merkel said the EU could not fully absorb Turkey as a member and is offering the country a sort of privileged partnership, short of membership.
"I think the integration capability, that is to say the absorption capability of the European Union, as it stands at the moment, is not sufficient to take on Turkey as a full member," Merkel said. "I am saying this to people today, and I also said this to the Turkish prime minister [Recep Tayyip Erdogan], and this interests people. We are saying this without being aggressive, but a lot of people agree with this."
Merkel's position has found favor among some Germans, who fear Turkish membership in the EU could lead to another large influx of Turkish immigrants. Germany is already home to more than 2 million Turks out of a population of 82 million people.
Schroeder, on the other hand, favors Turkish membership. He said that bringing Turkey into the EU will enhance Europe's security.
"If we manage to bind Turkey so closely to the West that it can't get away anymore, and through this we manage to combine a non-fundamental Islam with the values of the Western enlightenment in Turkey, then we in Germany and in Europe will gain security," Schroeder said.
Germany's relations with the United States soured badly after Schroeder refused to support the U.S.-led war in Iraq.
The White House is officially neutral in this contest, although some in the administration of President George W. Bush would clearly be happy to welcome Germany's first female chancellor into office.