The Social Democrat foreign minister, Frank-Walter Steinmeier, and his party’s leader, Vice Chancellor Sigmar Gabriel, wrote an article that appeared on Aug. 23 in the Frankfurter Allgemeine Zeitung — which generally favors the Christian Democrats — and laid out a 10-point program, including a common European code of asylum.

A senior German official, who requested anonymity to address a diplomatic issue, noted that the article had not been written with the interior minister, Mr. de Maizière, a Christian Democrat, in a clear effort to distinguish the Social Democrats in the minds of voters.

Ms. Merkel, who tends to weigh facts and public opinion carefully before declaring a position, clearly heard the message. She was also prompted to act by growing criticism from the far right of Germany’s acceptance of migration. Ms. Merkel was booed last week and called a “traitor” when she visited a shelter for asylum seekers in Heidenau, the site of violent anti-immigrant protests by neo-Nazis. Germany has said it expects up to 800,000 asylum seekers this year, prompting anxiety and political criticism, even though only 310,000 migrants and asylum seekers have reached Europe so far this year, according to the United Nations High Commissioner for Refugees.

There should be “no tolerance for those people who question the dignity of others, no tolerance for those who are not willing to help where legal and human help is required,” Ms. Merkel said, condemning violent protests as “shameful” and “vile.”

The German government said last week that Syrians would be allowed to apply for asylum in Germany, even if they entered the European Union through another country. Under the Dublin Regulation, asylum seekers are required to apply for protection in the first European Union country they reach.

The failure of the Dublin rules became part of this summer’s turmoil as enormous pressure mounted on Greece and Italy — nearly all 310,000 migrants this year have entered in those countries. Overwhelmed Greece and Italy — and now Hungary and other Balkan countries — are moving migrants through their countries to richer and more welcoming nations like Germany, Sweden and France.