'Start Here': Pelosi plans to send impeachment articles to Senate and protests in Iran over downed plane

Here's what you need to know to start your day.

It's Monday, Jan. 13, 2020. Let's start here.

1. Impeachment trial

House Speaker Nancy Pelosi is preparing to deliver the impeachment articles to the Senate within days and a trial could begin as early as this week.

"What happens there is a matter of some dispute at this point," ABC News' David Wright told "Start Here." "There's been some suggestions from the president's corner that the Senate could simply dismiss the case immediately, that they would ask the chief justice, John Roberts, who will be presiding over the Senate trial, to dismiss the charges because they claim they're unconstitutional."

In an interview on ABC's "This Week," Pelosi did not rule out the possibility of a House subpoena for testimony from former national security adviser John Bolton and other witnesses sought by Democrats, depending on whether the Senate seeks testimony in the trial.

2. Unrest in Iran

Iranian protesters took to the streets this weekend in anger over the government's delayed admission they mistakenly shot down a Ukrainian Airlines passenger jet, killing all 176 on board.

Tehran said "human error" led to the crash just hours after Iran fired more than a dozen missiles at U.S. military bases in Iraq, in retaliation for the American drone strike that killed Iranian commander Qassem Soleimani. But the government finally came clean on Friday.

ABC News' Somaye Malekian, who's based in Tehran, was at a protest in front of Amirkabir University of Technology: "It started with quiet -- a vigil ceremony, lighting up candles, putting up flowers in front of the photos, and then slowly turned out to become more like a protest... and at the end it was cracked down by the police throwing tear gas and it was not ended very peacefully."

3. Bernie momentum?

Just three weeks away from the Iowa caucuses, Sen. Bernie Sanders, I-Vt., holds 20% support among likely Democratic caucus-goers, according to a Des Moines Register/CNN/Mediacom poll, with Sen. Elizabeth Warren, D-Mass.; former South Bend, Indiana, Mayor Pete Buttigieg; and former Vice President Joe Biden following close behind.

"This is a team that's done this once before," ABC News Deputy Political Director MaryAlice Parks said. "The Bernie Sanders camp went through the caucus in 2016 so they came into 2020 knowing what it would take and they're delivering."

But it's still anyone's contest to win -- the poll also found that 45% of all likely caucus-goers say they could still be persuaded to support someone else.

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Elsewhere:

Royal emergency: The Meg-xit may come to a conclusion on Monday as Prince Harry and Duchess Meghan -- along with father Prince Charles -- meet with the queen to discuss the Duke and Duchess of Sussex's apparent exit from royal life.

Operation Carrot Drop: With 1 billion animals already lost to the wildfires in Australia, a group of rescuers spent the weekend airdropping tons of carrots and sweet potatoes to starving wallabies.

Retiring from stud: Diego the Galapagos giant tortoise gets around -- but no one is calling his promiscuity a bad thing. In fact, the tortoise is retiring from sex for very good reasons.

Unruly passenger: A man traveling from Washington, D.C., to Newark on a CommutAir flight apparently snapped last week, attacking a flight attendant and even injuring six police officers.

From our friends at FiveThirtyEight:

What To Watch For In College Football’s National Championship: After what seems like an interminable layoff, Clemson and LSU will hit the field in New Orleans tonight to decide the national champion.

Doff your cap:

Only 6 years old, John Oliver Zippay has endured a battery of medical procedures that would test even the most stoic adult.

John, nicknamed, "JO," was diagnosed with leukemia at just 3 years old.

After his final chemotherapy treatment, his elementary school classmates greeted him back to school with a hero’s welcome -- a standing ovation.