Kyrsten Sinema nearly walked out on Biden last year during a heated exchange over his economic agenda, book says

• Sen. Kyrsten Sinema almost walked out on Biden last year in a tense exchange over Build Back Better.
• The Arizona Democrat was angry with Biden for disclosing her spending demands in a White House meeting.

Sen. Kyrsten Sinema of Arizona almost walked out on President Joe Biden in the Oval Office during a tense exchange over the scope of his economic agenda, according to a forthcoming book from a pair of New York Times reporters.

The Dispatch first reported details of the back-and-forth between the pair. Insider also obtained a copy of the book "This Will Not Pass" ahead of its May 3 release.

According to authors Jonathan Martin and Alexander Burns, Biden strenuously sought to reconcile tensions between his party's centrist and progressive wings last summer around the size and scope of his domestic agenda. Progressives were pushing to go big on new social and climate programs while moderates tried restraining their ambitions and had fiscal concerns.

During a meeting with Democratic moderates, Biden revealed that Sinema had set her Build Back Better spending limit at $1.1 trillion — roughly one-third less than Sen. Joe Manchin's $1.5 trillion price tag.

Sinema appeared "visibly angry" at Biden for revealing details from their personal talks, Burns and Martin write. Biden aides had "feared that if Sinema drew a public red line at $1.1 trillion—a miserly sum by liberal standards—then the party would erupt in open war."

The authors wrote: "'Mr. President," she said, 'that was a private conversation.' Sinema began to stand up. She asked Biden: 'Do you want me to leave?'"

The president rushed to soothe tensions with the holdout. "If Biden resented her theatrics, he did not say so in the moment," Burns and Martin write. "He could not afford to lose her vote."

Spokespeople for Sinema didn't immediately respond to a request for comment.

"We respect that there will be no shortage of books written about the administration containing a wide variety of claims," a White House official told Insider on condition of anonymity. "We don't plan to engage in confirmations or denials when it comes to the specifics of those claims."

The tense exchange underscores the outsized influence that Sinema wields over the Democratic domestic agenda. Democrats can't advance a smaller version of their Build Back Better plan without unanimous support in the 50-50 Senate to overcome united GOP opposition.

Last year, Sinema flummoxed Democrats with her insistence to not negotiate in public and only dealing with the White House directly. Her opposition to raising corporate and income tax rates forced the party to abandon their efforts to unwind the 2017 Trump tax cuts, long a chief Democratic priority to attack inequality.

The Arizona Democrat recently said that she doesn't intend to switch up her demands in any upcoming negotiations over a smaller spending bill. Sinema has also said she remains strongly opposed to hiking tax rates on the rich and large firms, arguing that would damage their economic competitiveness.

"What I can't tell you is if negotiations will start again or what they'll look like," Sinema said at an Arizona Chamber of Commerce event last month. "But what I can promise you is that I'll be the same person in negotiations if they start again that I was in negotiations last year."