'Start Here': Iran war? 'I hope not,' Trump says. An SAT 'adversity score.' And De Blasio declares for 2020.

It's Friday, May 17, 2019. Let's start here.

1. 'Fearing'

On Thursday, President Donald Trump was asked directly: "Are we going to war with Iran?"

"I hope not," he said.

Lawmakers are looking for answers, especially after a New York Times report said the Pentagon had presented a plan to send 120,000 U.S. forces to the Middle East if Iran struck U.S. forces or resumed its nuclear program, says ABC News' Trish Turner.

"They're fearing that there's a move toward some sort of troop activity, military involvement in the Middle East," she says on "Start Here."

Next week, Secretary of State Mike Pompeo, Chairman of the Joint Chiefs Gen. Joseph Dunford and acting Defense Secretary Patrick Shanahan are set to conduct all-member classified briefings on Iran, according to congressional sources.

2. 'Context'

The College Board has announced SAT tests now will include an "adversity score" that takes into account factors including crime rates and poverty levels.

The new assessment tool -- called the Environmental Context Dashboard -- also will provide information on family income and where a student attended high school, but it won't include a test taker's race.

College Board CEO David Coleman tells "Start Here" this new component will provide "context" to the admissions process.

"Imagine a young person who has done so much with less," Coleman says. "Imagine what they'll do when they get to a resource-rich environment, like college."

3. 'Vulnerable'

The Tohono O'odham Nation, the third-largest Native American reservation in the U.S., is caught in the middle of a tense national debate over border security.

ABC News' Dan Harris details the challenges of the reservation and what he learned over the course of a year-long investigation for "Nightline."

"It has become, quietly but very seriously, a vulnerable spot in our national security," he says. "These folks, who are isolated and poor, have been targeted and systematically corrupted and co-opted by the largest drug cartel in the world -- the Sinaloa drug cartel."

4. 'Hey, why not me?'

Minutes after New York City Mayor Bill de Blasio announced on Thursday he was running for president, people questioned the decision.

On "Good Morning America," ABC News Chief Anchor George Stephanopolous noted a Quinnipiac poll that said 76% of New York voters didn't want the mayor to run for president, but de Blasio dismissed the data, saying, "I think you'd agree that the poll that matters is the election."

In such a crowded field of Democrats, what's prompting lesser-known candidates to run? FiveThirtyEight Editor-in-Chief Nate Silver thinks they may be eyeing other 2020 hopefuls, such as South Bend, Indiana, Mayor Pete Buttigieg, who overcame a lack of name recognition to rise in the polls.

"They see Donald Trump having risen against the odds to win the GOP nomination last year," Silver tells us, "and they say, 'Hey, why not me?'"

"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.

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Doff your cap:

Nearly 16 years ago, a college student was found dead after a night of partying in Brooklyn, New York. Two men were charged with his murder, but one of them, John Giuca, had his conviction overturned last year.

And yet, Giuca remains behind bars at New York City's Rikers Island Jail, with his fate still hanging in the balance. He's long maintained his innocence.

"I had nothing to do with the murder of Mark Fisher," Giuca told "20/20." "I want my name cleared. One of the worst parts about this is people thinking that I'm a murderer. And I want that wiped away because it shouldn't be there in the first place."

Since the day her son was arrested, Doreen Giuliano has been on a crusade to prove his innocence, even tracking down jurors from his trial and secretly recording conversations with them.

"John is innocent, and we can prove it," she said. "They put away an innocent man, and there's nothing that's going to stop me."

Their story on "20/20" airs TONIGHT at 9 Eastern on ABC.