Good morning, NBC News readers.

Kirstjen Nielsen's tumultuous tenure as head of the Department of Homeland Security ended with a presidential tweet on Sunday.

Here's what else we're watching today.

Nielsen quit after meeting with Trump

The embattled homeland security secretary resigned amid mounting frustration by President Donald Trump over his own administration's failure to stop the flow of migrants into the country.

After a meeting at the White House on Sunday, Trump announced on Twitter that Nielsen would be leaving her post. She issued a resignation letter a few minutes later.

Nielsen, 46, had tepid support within the Trump administration, despite being the public face for many of the president's deeply divisive anti-immigration policies.

Kevin McAleenan, the current commissioner of Customs and Border Protection, will become acting secretary pending confirmation of Nielsen's successor, Trump tweeted.

Inside Trump's all-about-that-base 2020 strategy

Just like his 2016 campaign and his presidency, Trump's 2020 reelection campaign will be unconventional.

The idea is for the president's campaign to identify and mobilize a new set of pro-Trump voters who typically don't go to the polls, rather than build from his base like a traditional politician, NBC News' Jonathan Allen writes.

"There is going to be nothing normal about the way this president campaigns," said Trump ally Rep. Mark Meadows, R-N.C.

'You can burn a building, but you can’t take us, can’t break us.'

Three historic black churches in the same Louisiana parish have gone up in flames in 10 days.

"We believe that the three fires obviously are not coincidental, they are related," Louisiana State Fire Marshal "Butch" Browning said.

But on Sunday, members of the local congregations prayed together in a defiant show of unity.

“Let them know we’ll keep praying with a building or without a building,” said Morning Star Baptist Church Deacon Curtis Zachary.

Firefighters and fire investigators responded to a fire at Mt. Pleasant Baptist Church in Opelousas, Louisiana, last Thursday. Leslie Westbrook / The Advocate via AP

Israel's Netanyahu aims to make history

Prime Minister Benjamin Netanyahu is pulling out all the stops to convince voters that he is the man who can keep Israel great ahead of Tuesday's election.

After a decade in power leading a series of right-wing governments, a vital part of Netanyahu’s campaign sits 10,000 miles away in Washington: Donald Trump.

However, Netanyahu and his Likud party are being severely tested by Benny Gantz, a general former chief of staff of Israel's military.

If Netanyahu wins, he will embark on his fourth consecutive and fifth overall term and become Israel’s longest-serving prime minister, surpassing the country’s founding father David Ben-Gurion.

Here is a primer on the looming showdown as Israelis prepare to go to the ballot box.

Want to receive the Morning Rundown in your inbox? Sign up here.

Plus

'Thank God they were at the right place at the right time': A youth volleyball team saved a woman dangling from a bridge and prevented a possible suicide.

Her Majesty's Secret Service: Prince William went undercover with Britain's spy agencies for three weeks.

'A kind of war': Democratic presidential candidate Pete Buttigieg described his personal struggle with sexual orientation in an emotional speech.

Baylor beat Notre Dame to win their third NCAA women's title.

Baylor celebrates on Sunday. Jasen Vinlove / USA TODAY Sports - Reuters

Like political news in your inbox? Want fresh analysis on the White House and 2020 every morning? Sign up for our redesigned Meet the Press: First Read newsletter here.

THINK about it

Kim Kardashian has done more to expose detox tea lies than the FDA, S. Bryn Austin, a professor at Harvard's School of Public Health.

Science + Tech = MACH

NASA's $17-billion moon rocket may be doomed before it ever gets to the launch pad.

NASA's Space Launch System, seen in this artist's rendering, is billed as the world's most powerful rocket. But its development has fallen three years behind schedule — and is way over budget. NASA

One fun thing

ICYMI: "Saturday Night Live" poked fun at former Vice President Joe Biden and allegations that he has invaded women's personal space over the years.

Former "SNL" cast member Jason Sudeikis, who returned to portray Biden, said he'd been inspired by U.S. Sen. Elizabeth Warren, D-Mass., to take a DNA test to discover his roots.

"It turns out that I’m one percent Eskimo, so I’m allowed to do the [nose] kisses," he said.

Thanks for reading the Morning Rundown.

If you have any comments — likes, dislikes — drop me an email at: petra@nbcuni.com

If you want to receive the Morning Rundown in your inbox Monday through Friday, please sign up here.

Thanks, Petra