Good morning, NBC News readers.
An unwelcome player takes center stage in President Donald Trump's impeachment drama, Democrats hit the final stretch before the Iowa caucuses and fans all over the world mourn Kobe Bryant’s death.
Here's what we're watching this Tuesday morning.
Trump's defense focuses on Bidens as calls for Bolton testimony grow
Trump's lawyers presented the thrust of their defense in the Senate impeachment trial Monday.
They insisted there was nothing improper about Trump's dealings with Ukraine's government and tried to steer the focus to questions about the conduct of former Vice President Joe Biden and his son Hunter Biden.
They also largely avoided the elephant in the room: An explosive report that former national security adviser John Bolton says in an unpublished book that the president personally tied aid for Ukraine to an investigation into the Bidens. Bolton's account directly contradicts the president's version of events.
Besides, Trump's defense lawyer Alan Dershowitz argued, even if the reported Bolton allegations were true, there was "nothing" impeachable about them.
- Recap: Here are six key takeaways from the sixth full day of the Senate impeachment trial.
- Who leaked Bolton's book? Not us, insists Bolton's team. They tell NBC News that they provided the White House with a single copy of the manuscript to undergo a national security review and that any copies were made inside the White House. (Video)
- Analysis: Bolton's revelations have made it a lot harder for GOP senators to give Trump the cover he's looking for in his impeachment trial, writes NBC News' Jonathan Allen. "Bolton's thumb has tilted the scale," says one GOP fundraiser who supports Trump.
- Back at it: The Senate proceedings will resume at 1 p.m. ET. Watch on NBC, MSNBC and follow our live blog for updates and analysis.

Crash investigators looking at weather conditions during Kobe's last flight
Federal investigators looking into the helicopter crash that killed NBA star Kobe Bryant, his teenage daughter and seven other people, will focus on the poor flying conditions in the Los Angeles area, the possibility of human error or a technical malfunction, aviation experts say.
The suddenness of the Bryant's death is taking a toll on fans and friends alike.
LeBron James posted about grappling with the grief and heartache he was feeling about losing his dear friend — especially after just speaking to him on Sunday morning.
"I'm heartbroken and devastated my brother!!" the NBA legend wrote on Instagram.
James' feelings were shared by fans all over the world — from China to Italy, his childhood home.
The NBA announced that it would postpone a Lakers-Clippers game scheduled for Tuesday at the Staples Center in Los Angeles "out of respect for the Lakers organization, which is deeply grieving" the loss of their longtime player.

'Women win': Warren takes on gender in final stretch before Iowa caucuses
With less than a week before the Iowa caucuses — and amid an unsteady standing in the polls — Sen. Elizabeth Warren is leaning in on the gender question.
"I just want to be clear: Women win!" she declared Sunday night to cheers in Cedar Rapids.
Meantime, mainstream Democrats are grappling with the fact that progressive candidate Sen. Bernie Sanders has taken the lead in several recent surveys of Iowa and New Hampshire.
A Sanders win would turn the Democratic Party upside down, much as Trump's victory did for the GOP in 2016
"We are their worst nightmare," Sanders said about the Democratic establishment on Sunday.
An ER doctor was charged with abusing his baby. But 15 medical experts say there’s no proof.
Last year, Dr. John Cox brought his 1-month-old daughter to the hospital, saying he’d fallen asleep while holding her and wanted to make sure she wasn’t hurt.
He was shocked when staff at Children’s Wisconsin, where he worked in the ER, reported his daughter’s tiny bruises as abuse.
Even though other doctors disputed the evidence, Cox and his wife lost custody of their daughter, and last week he was charged with abusing her.
A dozen of Cox’s co-workers say they’re alarmed by what happened to him, and they fear that the hospital’s child abuse team is "out of control," needlessly reporting parents to Child Protective Services.
"This is a disease in our hospital," one physician said.
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Plus
- The coronavirus death toll spikes in China as U.S. plans to evacuate citizens from epicenter.
- The State Department booted an NPR reporter from an upcoming trip after a spat with Secretary of State Mike Pompeo.
- What is Byte? The internet's new old-school, short-form video app.
- NFL Twitter accounts have been hacked, including those of Super Bowl-bound Chiefs and 49ers.
THINK about it
Kobe Bryant died an inspiration to many — but not all. And we can't ignore why, sports writer Will Leitch argues in an opinion piece.
Shopping
Hosting a Super Bowl watch party? We've got tips on TV deals and other gear to take your party to the next level.
Quote of the day
"I'm Not Ready but here I go."
— NBA star LeBron James describing his grief and heartache over the loss of his friend Kobe Bryant.
One fun thing
First, it was an unexpected appearance at Trump's impeachment hearings, and now it’s a barrier-breaking debut during one of the year’s most watched sporting events.
Drag queens will grapple with "helmet hair" in a new ad— during Super Bowl LIV.
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Thanks, Petra
