'Start Here': Trump kicks off 2020 campaign as his defense pick steps down Here's what you need to know to start your day.

It's Wednesday, June 19, 2019. Let's start here.

1. Trump 2020

President Donald Trump officially launched his 2020 campaign on Tuesday night with a massive rally in Orlando, Florida.

He spent much of the address alternating between blasting Democrats and the Russia "witch hunt," while also making his case for reelection.

"Our patriotic movement has been under assault from the first day," Trump told the crowd. "We've accomplished more than any president has in the first 2 1/2 years and under circumstances that no president has had to deal with before … nobody has done what we have done."

With Election Day more than 500 days away, ABC News Chief White House Correspondent Jonathan Karl was in Florida gauging the support of Trump voters in the key battleground state, and he shares his insights today on "Start Here."

2. 'Securing our nation against threats'

Acting Defense Secretary Patrick Shanahan is withdrawing from the Senate confirmation process after graphic domestic violence incidents involving his family surfaced in media reports.

In a Pentagon statement issued Tuesday, Shanahan said: "The confirmation process should focus on securing our nation against threats, readiness and the future of our military, and ensuring the highest quality care and support for service members and their families."

The president thanked Shanahan for his service on Tuesday and said he "has done a wonderful job." Trump named Army Secretary Mark Esper as the new acting defense secretary, and lawmakers will need to approve his confirmation.

Shanahan's resignation comes as tensions with Iran are heating up. Trump told reporters the U.S. is "very prepared" for Iran "regardless of what goes," but the acting secretary's departure has caught the Department of Defense at a "tense time," according to ABC News' Elizabeth McLaughlin.

"This job has now been vacant for over six months," McLaughlin says, referring to when James Mattis stepped down. "It's pretty unprecedented. There are so many roles that are now vacant or filled by acting people here at the Department of Defense."

3. 'Original sin'

A House panel is set to hold a hearing today on reparations as several Democratic presidential hopefuls have voiced their support for compensating descendants of slaves.

"America cannot be made whole until we clean up certain issues from our past," Marianne Williamson, one of the most vocal 2020 candidates on the issue, says on "Start Here."

Senate Majority Leader Mitch McConnell said on Tuesday he was opposed to paying reparations because "we've tried to deal with our original sin of slavery by fighting a civil war, by passing landmark civil rights legislation, by electing an African American president."

4. 'Victory for truth and decency'

Lenny Pozner, father of a Sandy Hook victim, has won a defamation lawsuit against a conspiracy book's authors who claimed the murders of 26 children and adults, including Pozner's 6-year-old son, Noah, never happened.

Pozner reached a separate settlement with Moon Rock Books, the publisher of "Nobody Died at Sandy Hook," to pull the books from shelves, and the publisher's principal officer apologized to Pozner's family.

In a statement to ABC News, Pozner said the ruling is "a victory for truth and decency" and "an important turning point for victims of hoaxers and online harassers."

The lawsuit has been part of an ongoing battle Sandy Hook families and others of mass-casualty tragedies have to fight against "hoaxers," according to Anna Merlan, author of "Republic of Lies," who says these families "are deluged with people telling them that the event was a hoax, that it was a cover-up ... and they deal with years and years and years of harassment."

"Start Here," ABC News' flagship podcast, offers a straightforward look at the day's top stories in 20 minutes. Listen for free every weekday on Apple Podcasts, Google Podcasts, iHeartRadio, Spotify, Stitcher, TuneIn or the ABC News app. Follow @StartHereABC on Twitter, Facebook and Instagram for exclusive content and show updates.

Elsewhere:

'Videos and photographs': A teen in Alaska is accused of killing a friend after a man online promised her $9 million to "rape and murder someone" -- and document it.

'Concentration camps': AOC and some Republicans disagree on what to call the mass detention of civilians who aren't being brought to trial.

'A spiral of depression': A 53-year-old man gets seven years in prison after engaging in sexual activity with a 15-year-old girl on his private plane.

From our friends at FiveThirtyEight:

Turns out the NL East didn't have 4 good teams: It's looking like a two-team race between the Braves and Phillies.

Doff your cap:

Paige Winter, 17, was rushed to the hospital after she was attacked by a shark in Atlantic Beach, North Carolina, on June 2. Her left leg was amputated at her thigh, and she lost two fingers.

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Doctors who treated her at Vidant Medical Center describe how they assessed her injuries and why her positive outlook has been so important to her recovery.

"Paige is alive as a result of one of the strongest forces that I have encountered in 20 years as a trauma surgeon, surpassing any medical technology," said Dr. Eric Toschlog, the chief of Trauma and Acute Care Surgery at Vidant Medical Center and a professor of Surgery, Brody School of Medicine at East Carolina University. "She was saved by love -- the love of a father for his daughter."