The CDU has seen its support eroded by the far-right Alternative for Germany, which has profited from popular concern about the influx into Germany in 2015 of around a million refugees, many fleeing war in the Middle East.
Chancellor Angela Merkel will rally her conservatives at a party conference on Tuesday to gird for a German election in 2017 that she expects to be "tough like no other".
Seeking a fourth term in office, Merkel must unite her Christian Democrats (CDU) and try to recapture some of her personal popularity, undermined by the crises that have rocked Europe.
Italian Prime Minister Matteo Renzi's referendum defeat on Sunday and the impending departure of French President Francois Hollande underline Merkel's status as Europe's most experienced leader, but she needs to win back disgruntled voters at home.
The CDU has seen its support eroded by the far-right Alternative for Germany (AfD), which has profited from popular concern about the influx into Germany in 2015 of around a million refugees, many fleeing war in the Middle East.
"We know our world is changing. It always has been. Anyone who promises to be able to stop that isn't being honest," said Peter Tauber, Secretary General, CDU. "What we are promising is to turn this change in a good direction for our country.", he added.
With Britain poised to leave the European Union (EU), Russia testing the North Atlantic Treaty Organisation (NATO) alliance and southern Europe's economies struggling, the CDU will debate a main resolution entitled: "Orientation in difficult times - for a successful Germany and Europe".
The conference is in Essen, a former industrial hub where unemployment is at 11.6%, twice the national average. It is where Merkel was first elected CDU party chairwoman in 2000.
Returning to Essen, Merkel, aged 62 and chancellor for 11 years, must rally her party to fight off the social media-savvy AfD while also appealing to the centre ground.
Since declaring in November, she would seek a fourth term, her conservatives have gained support. A survey by pollster Emnid published on Sunday showed support for the conservative bloc - Merkel's CDU and its Bavarian sister party, the Christian Social Union (CSU) - rising by 2 points to 37%, the highest level since January.
With her current Social Democrat coalition partners trailing 15 points at 22% as her nearest rivals, Merkel is likely to win the election next September. But coalition building could then prove difficult, with the AfD likely to enter the national parliament for the first time.
"In Essen, we need to move into fight-mode," said one CDU official.
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