On Tuesday, the impeachment battle escalated when Republican Senator Lindsey Graham invited the president's lawyer, Rudy Giuliani, to testify about allegations of corruption involving the Bidens. The administration blocked Gordon Sondland, the U.S. ambassador to the European Union, from appearing before a House panel. Nancy Cordes reports.

President Trump's fight against the House impeachment inquiry is turning into a battle royal. In a letter to top congressional Democrats, the president's White House counsel called their inquiry "unconstitutional" and said Mr. Trump will not cooperate. The White House is daring House Speaker Nancy Pelosi to call for a vote on impeachment or take the president to court. Nancy Cordes reports.

Chief Washington correspondent Major Garrett joins “CBS This Morning” from Washington to discuss why the White House wants House Speaker Nancy Pelosi to hold a formal vote for an impeachment inquiry into President Trump.

Members of Congress from both parties are voicing their opinions on the impeachment inquiry into President Trump at town halls in their home districts. For some Democrats in mostly Republican districts, their approach has to be measured. Politico Congressional Reporter Andrew Desiderio followed Democratic Illinois Congressman Sean Casten to six of his town halls to see how he's handling the issue. Desiderio joined CBSN to discuss what he saw.

This week on "Face the Nation," Margaret Brennan, in Syria, a shaky ceasefire brokered by the U.S. is set to expire Tuesday while the White House continues defends itself against impeachment calls.

Former Vice President Joe Biden has announced his support for the impeachment inquiry against President Trump for the first time. Ed O'Keefe reports.

CBS News was first to learn the full contents of a memo written by the whistleblower at the heart of the House impeachment inquiry. It was based on a conversation with a White House official who listened to the July phone call between President Trump and Ukraine's leader. Major Garrett reports.

CBS News is revealing details from a memo written by the whistleblower whose claims led to the House impeachment inquiry into President Trump. Mr. Trump has maintained the entire report is a "scam," pointing to the person being a registered Democrat. CBS News has learned the whistleblower has a prior working relationship with a current Democratic presidential contender, but lawyers say their client has never worked for or advised a political campaign or party. Weijia Jiang reports.

Republican Sen. Rand Paul is backing President Trump's decision to withdraw U.S. troops from northern Syria. The Kentucky lawmaker, who ran against Mr. Trump in the 2016 election, has become a supporter of his foreign policy. Paul joins “CBS This Morning” in his first TV interview to discuss his new book, "The Case Against Socialism."

The White House is pushing back against House Democrats' impeachment inquiry, escalating the fight between the two branches of the government. In a letter, the Trump administration called it unconstitutional and a violation of due process. CBSN legal contributor Keir Dougall, a former assistant U.S. attorney for New York's eastern district, joined CBSN to discuss where the Trump administration's argument stands legally.