Many Democratic lawmakers say they’ll decide on impeachment after they learn the details of a call between President Trump and Ukrainian President Volodymyr Zelensky that was the subject of a whistleblower complaint.

The number of House Democrats who support impeaching the president increased this week, and many Democrats said their decision hinges on whether there is proof that Trump offered billions in security aid to Ukraine if Zelensky would pledge to investigate Trump’s chief political rival, Joe Biden.