The Smart Brevity on last night: Joe Biden survived but didn't dominate.

• The former vice president rebounded, "but barely so and perhaps by opening himself up to future criticisms," as the WashPost's Dan Balz put it.
• The narrative after the back-to-back nights: "Biden and Elizabeth Warren ... are two high-speed trains on a collision course," per Reuters' James Oliphant.

A Biden adviser tells me: "[I]t was everybody versus Biden ... Never threw a first punch, but didn’t let himself be a punching bag."

• Jimmy Kimmel: "It was 'Joe Versus the Volcano.'"

Sen. Kamala Harris of California has established herself as a frontrunner, Axios' Alexi McCammond reports from the debate site:

• She did that by attacking Biden in the first debate, which led to attacks on her from every side of the stage last night.
• That meant more scrutiny of her record, but she was calm and ready for the attacks. 

No matter what anyone said, Harris turned the fire back on Biden, Axios' Alayna Treene adds.

• Unlike the previous night, when Warren and Bernie Sanders refused to take the bait from the moderators to go after each other, Harris and Biden went in on each other — criticizing the other's health care plan — right out of the gate.

Another good night ... Cory Booker arguably surpassed Harris as Biden's primary antagonist, Axios' Zach Basu writes in his "4 big takeaways":

• Booker attacked Biden for refusing to condemn the high number of deportations carried out under the Obama administration: "You invoke President Obama more than anybody in this campaign. You can't do it when it's convenient and dodge it when it's not."

Trump campaign statement: "Another win for President Trump."

• Go deeper.

The debate showed Joe Biden's long career has its liabilities, Axios managing editor David Nather writes:

• The pile-on covered everything from his Senate years (Kirsten Gillibrand attacking him for a 1981 op-ed about "deterioration of the family") to his years as President Obama's vice president (Bill de Blasio on deportations) to his moderation (Kamala Harris on his health care plan, Jay Inslee on his climate plan).

Biden had to step back from Obama:

• He suggested that he wouldn't continue deportations at Obama's level ("Absolutely not") and said he wouldn't rejoin the Trans-Pacific Partnership in its previous form ("I'd renegotiate").
• He's rethinking his Senate record, too. And sometimes it's awkward. Biden has already reversed his previous support for the Hyde amendment, which bans the use of federal funds to pay for abortion, but this time he claimed that "everybody" in Congress "has voted for the Hyde amendment at some point."
• He acknowledged that "I did make a bad judgment, trusting the president" (zing!) in supporting George W. Bush's Iraq war.

P.S. An unrehearsed moment ... As Biden and Kamala Harris greeted each other onstage, he could be heard saying: "Go easy on me, kid."

What we talked about ...

... and what we wondered:

Former Energy Secretary Ernie Moniz and former Sen. Sam Nunn — co-chairs of the nonprofit Nuclear Threat Initiative — give Axios readers a sneak peek at a big talker they have coming in the September/October issue of Foreign Affairs:

• "Not since the 1962 Cuban missile crisis has the risk of a U.S.-Russian confrontation involving the use of nuclear weapons been as high as it is today."

Wait! What?

Even after decades of reducing their arsenals, the United States and Russia still possess more than 90 percent of the world’s nuclear weapons — over 8,000 warheads, enough for each to destroy the other, and the world, several times over ...

[A]rms control has withered, and communication channels have closed ... [O]utdated Cold War nuclear postures have persisted alongside new threats in cyberspace and dangerous advances in military technology (soon to include hypersonic weaponry, which will travel at more than five times the speed of sound). 

Why it matters: "The United States and Russia are now in a state of strategic instability; an accident or mishap could set off a cataclysm."

• "Yet unlike during the Cold War, both sides seem willfully blind to the peril."

Full article posts next week.

Amazon has made a series of investments, acquisitions and R&D moves in the smart home industry, allowing it to capture first-mover advantage in "surveillance capitalism," one of the most important new markets on the planet, writes Axios' Erica Pandey.

• Why it matters: Its dominance in smart devices and services could grant the Big Tech giant unchecked access to the data-rich interiors of our homes, making it "extremely inexpensive … to record some of the most intimate parts of your life," says Meredith Whittaker, co-founder of the AI Now Institute.

Speaking to Axios, Amazon says that its speakers and cameras can be turned off at will and come with lights that signal when they are recording. It also says customers can log onto portals and delete whatever they want.

By this time next year, AT&T’s WarnerMedia, Comcast’s NBCUniversal, Disney and Apple will all have streaming video services, taking on Amazon, CBS, Hulu and Netflix, Bloomberg Businessweek's Felix Gillette and Gerry Smith write:

• Why it matters: "It’s unlikely that any of these media and tech giants will escape this looming showdown unscathed. Even the ultimate winners are expected to limp into the future bloodied and battered. "
• Jamyn Edis of NYU's Stern School of Business: Next year "is shaping up to be 'The Hunger Games' for the streaming services."

The bottom line: "The success of Netflix’s model — charging a monthly fee for a large amount of ad-free, on-demand programming ... — has inspired millions of people to cancel their pay-TV service and get their home entertainment online."

Democrats in Iowa and Nevada want to boost participation in next year's caucuses by opening them up to telephone voting. Hacking-spooked Democrats have worked to protect the process from interference, but some experts still see notable risks, Axios cybersecurity expert Joe Uchill writes.

• Why it matters: Security concerns have long troubled digital voting systems.
• Many of the same problems with online voting carry over to phone voting.

Caucuses are complex processes, typically requiring hours of participation by each voter. That’s prohibitive for many, especially in places like Las Vegas, where a tourism-based economy forces many to work non-standard hours.

• The DNC this year issued a directive to allow for absentee voting.

The state parties are taking steps to limit the phone vulnerabilities: Both states will require in-person signup to receive credentials for the phone caucus.

• Iowa plans independent vetting of the system, giving the public a chance to demonstrate security flaws in the system before caucus day.
• That’s more than can be said for most in-person voting machines.

The bottom line: Doubts fueled by an angry runner-up could endanger public confidence.

President Trump's rally in Cincinnati this evening will be a test for both candidate and crowd, AP notes:

• It's the first Trump rally since his audience chanted "Send her back!" on July 17 in North Carolina.

Woodstock 50, marking this month's 50th anniversary of the groundbreaking 1969 festival, is officially canceled, AP music writer Mesfin Fekadu writes:

• Holdups for the three-day festival included permit denials and the loss of a financial partner and a production company.
• Jay-Z, Dead & Company and John Fogerty announced last week that they wouldn't perform, after organizers moved the event from Watkins Glen, N.Y., to Merriweather Post Pavilion in Columbia, Md.

Woodstock will still celebrate 50:

• Ringo Starr, Santana and John Fogerty will perform at a smaller anniversary event at Woodstock's original site in Bethel, N.Y.

While most of the other candidates finished their closing statements at last night's debate by giving their website addresses, Joe Biden tried to get fancy:

• "If you agree with me, go to joe30330 and help me in this fight."
• What he meant: Text JOE to 30330.

The internet, of course, figured it out right away and let it slide.