From today’s Bloomberg Politics’ Balance of Power opener by Kate Hunter:

The world’s last line of defense against Donald Trump’s “America First” doctrine is gone. Defense Secretary Jim Mattis’s abrupt resignation is sparking fears that there’s no one left to restrain the president’s most combative and isolationist impulses amid his rapid-fire moves to reshape the U.S. military footprint abroad.

Already the floodgates are opening, Nick Wadhams writes.

U.S. forces in Syria will be quickly withdrawn — the very issue that provoked Mattis’s resignation — as the president declares victory over Islamic State.

American troop levels in Afghanistan will be slashed in half even as peace talks founder. Both decisions signal Trump’s willingness to abandon key allies on the battlefield. Read the resignation letter here.

In a Washington that had grown accustomed to White House chaos, this week’s developments forced even Trump’s most robust defenders to question his thinking. Senate Majority Leader Mitch McConnell — usually loathe to criticize the president — said he was “distressed” over the departure of Mattis, who he said had a “clear-eyed understanding of our friends and foes.”

McConnell’s comments underscore how perilous even Trump’s Republican brethren view the U.S. position as the president heads into 2019 increasingly left to his own devices.

More: Mattis Resignation Puts Trump’s Presidency in Peril (Bloomberg Opinion – Eli Lake) Donald Trump may not know it yet, but his presidency is collapsing.

Howard Wolfson on Mike Bloomberg: “You don’t get to be as successful as he has shying away from fights or being intimidated by people” (CNN – The Axe Files)

Mike Bloomberg “has stood toe to toe with a lot tougher characters as mayor of New York, as a business leader,” Wolfson told David Axelrod on his Axe Files podcast. “He is not going to be afraid of Donald Trump.”

“So many of the issues that [Bloomberg] has spent a lifetime fighting for — whether it be gun safety, or the work on climate, or taking on the Big Tobacco consortia, or educational equity and opportunity, job creation — all of those things are under threat by this administration,” he said.

“There’s a lot more you can do as president than you can as a philanthropist. As great as his philanthropy is, if [Bloomberg] decides to run, it will be for that reason,” he said.

Markets Today:
-As Stocks Drop, Trump Fears He’s Losing His Best Argument for Reelection (Washington Post)
-Wild Days Return to Stock Market as VIX Surges Like Never Before (Bloomberg)

Tobacco Watch: Juul Closes Deal with Tobacco Giant Altria (New York Times)

@MikeBloomberg tweeted that the deal “reveals e-cig companies are taking a page from the tobacco industry playbook – deeply concerning as 3.6M middle and HS students are now vaping regularly. @US_FDA must pull flavored e-cigs & prohibit marketing to kids.”

Weekend reads.

When Mark Cuban needed help cleaning up a #MeToo Mess at the Dallas Mavericks, he turned to Cynthia Marshall (Bloomberg Businessweek cover)

More on the Brexit Short: For Farage and Brexit Pollster, a World of Gamblers and Gambling (Bloomberg) The odds were long against the Leave campaign, but the men around Nigel Farage somehow came up winners.

Travel Section: Gatwick’s Drone Debacle Should Be a Wake-Up Call (Bloomberg Opinion Editorial) Defending against wayward UAVs is a serious challenge. Technology can help.

DNA Test Surprises: Results Are Turning AncestryDNA Customer-Service Reps Into Therapists (Bloomberg) How do you tell someone that her brother is not her brother?

Book section: Bloomberg Markets Editor Christine Harper Co-Authors Paul Volcker Memoir that Tops “Best of 2018” Lists (Bloomberg press announcement)
The Financial Times called the book “a testament of the most important official working in economic policy of the last generation.”

Bloomberg’s Year in Photos: It was a year of populist rebellions and political stare-downs as women gained power. Trade patterns were upended and long-standing bans were lifted. And through it all, the world still managed to provide moments of wonder. Click here for some of Bloomberg’s best news photos of 2018.

Best of late night.

On the resignation of U.S. Defense Secretary James ‘Mad Dog’ Mattis:

“It’s kind of scary when everyone says, ‘Oh, there goes the voice of reason, Mad Dog.’”
–Stephen Colbert

On the possible U.S. government shutdown tonight:

“Hundreds of thousands of workers won’t get paid. Basically, Trump is taking paychecks from federal employees at Christmastime to punish Congress for not paying for a wall he swore 500 times Mexico would be paying for. So, Feliz Navidad, everyone.”
— Jimmy Kimmel

“I saw that Google has a Santa tracker where you can watch Santa’s journey around the world. Yeah, not to be outdone, Facebook has a tracker where you can steal Santa’s social security number.”
— Jimmy Fallon

For more best of late night from the New York Times, click here.