What You Need to Know: Top diplomat revises his testimony

WASHINGTON (AP) — For only the fourth time in U.S. history, the House of Representatives has started a presidential impeachment inquiry. House committees are trying to determine whether President Donald Trump violated his oath of office by asking Ukraine to investigate political rival Joe Biden and his family and to investigate the country's involvement in the 2016 U.S. presidential election.

A quick summary of the latest news and what's to come:

WHAT YOU NEED TO KNOW

—In a striking reversal, a top diplomat revised his testimony in the House impeachment inquiry to acknowledge that U.S. military aid to Ukraine was being withheld until the foreign ally promised to investigate corruption as President Donald Trump wanted.

—Partisans of all stripes invariably will use Tuesday's elections in four states for clues about how voters are reacting to the impeachment saga

—Marie Yovanovitch, the ousted U.S. ambassador to Ukraine, says she raised concerns about the Trump administration's actions in Ukraine and the reports in U.S. media against her with Gordon Sondland, the U.S. ambassador to the European Union. In response, he encouraged her to tweet her support for Trump on social media.

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WHAT'S NEXT

The State Department's David Hale is expected to provide a deposition on Wednesday, while Russ Vought, acting director of the White House Office of Management and Budget, and Energy Secretary Rick Perry are not expected to appear.

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NUMBERS THAT MATTER

If Trump is impeached, the narrowly divided and increasingly partisan Senate would need 67 votes to convict and remove him from office. There are 53 Republicans in the Senate; Democrats would need 20 GOP defections, assuming all 45 Democrats and two independents who caucus with them vote to convict.

This AP-produced primer explores the Senate trial process based on precedents set when President Bill Clinton was impeached:

https://youtu.be/OpEwv-LPX3E

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WORTH READING

Newly released transcripts from diplomats Kurt Volker and Gordon Sondland, which includes a three-page addendum revising some of Sondland's testimony from October:

Sondland: http://apne.ws/8NmlA02

Volker: http://apne.ws/rTdEmG4