US president's son cites an article from far-right outlet Breitbart, violating the strict conventions in place to protect officials who reveal wrongdoing in government

Taylor gives new account of quid pro quo central to impeachment probe, describing Trump's demand that 'everything' Zelenskiy wanted hinged on public vow to investigate Democrats

President tweets that he won't allow ambassador to testify before 'a totally compromised kangaroo court;' Schiff calls move further evidence of obstruction of Congress