Last week, a Christian Democratic Union (CDU) motion for stricter migration policies passed only with support from the far-right Alternative for Germany.
That's planted seeds of distrust among the other parties in parliament, parties that Friedrich Merz needs to keep on side for coalition talks after the election.
Conservative figures are adamant that they will not work with the far right.
"No, no, no to any cooperation with the AfD. We will not help the AfD. We will fight them," said Markus Söder, leader of the CDU's Bavarian sister party, the CSU.
But we've been here before. The Alternative for Germany has been building up support in recent years and has practically cemented itself in second place behind the conservatives in the polls.
Despite the party breathing down his neck, Friedrich Merz is adamant that he won't change his mind.
"We will not work with the party that calls itself the Alternative for Germany. We haven't before, we won't in the future. Not ever. This party goes against everything that our party and our country has built in recent years and decades in Germany," he said.
Merz is hoping to win the election by taking a tougher stance on migration — one of the biggest issues in the campaign — with just three weeks to go until Germans cast their votes.