Cracking the Sinema code

• In conversation with colleagues, she’ll suggest that her top priority is passing the $1.2 trillion bipartisan infrastructure deal she brokered this spring over late-night, wine-fueled negotiations. Beyond that, you're piecing together clues.
• President Biden and his top aides met her four times over the course of a day this week without totally cracking the code.
• Sinema on Thursday tweeted a statement saying, "Claims that the Senator has not detailed her views to President Biden and Senator [Majority Leader Chuck] Schumer are false" and they "are fully aware of Senator Sinema's priorities, concerns and ideas."

Between the lines: Progressives could be forgiven for presuming that Sinema, 45, the first openly bisexual member of Congress, who's easy to spot in her trademark sleeveless dresses, wry wigs and acrylic glasses, would share their woke politics.

• They've been befuddled, and increasingly enraged, when she behaves more like the late Republican Sen. John McCain, another Arizonan who didn't mind challenging party orthodoxies.
• At her core, Sinema is something of a fiscal conservative, which disappoints progressives, leading them to whisper about a primary challenge in 2024.
• She's unconventional (see: recent internship at a Sonoma winery) and a force to be reckoned with. She's known to rise between 4-5 a.m. to train for her next race, and she was forced to take up aqua jogging after breaking her foot this summer in something called the "Light at the End of the Tunnel Marathon."

The big picture: While Manchin has been intensely focused on the price tag of spending, setting his limit at $1.5 trillion, Sinema has signaled she's more concerned with the tax side of the equation, including who pays them.

• She’s suggested to some allies that she’s reluctant to support any increase in the corporate tax rate, but she’s more likely to accept a smaller increase to the headline rate — likely in the 24% range, well short of Biden's proposed 28%.
• She's raised flags about increasing the rate on corporations' international profits, which she believes could harm their competitiveness.
• On capital gains, she’s also indicated that she’s opposed to Biden’s headline 39.6% rate but could accept a number in the mid-twenties.

Flashback: Her infrastructure package relied on creative accounting to fund the new $550 billion in additional spending, including $60 billion in dynamic scoring.

• She’s open to the arguments from some of her old centrist friends in the House, like Rep. Stephanie Murphy (D-Fla), that spending to fight climate change doesn’t need to be offset.

A trained social worker who relied on Pell grants in college, Sinema believes in the power of government to help lift people from poverty.

• That aligns her with Biden’s spending plans to help poor families, including the expanded Child Tax Credit, lowering child care costs, and free preschool.
• She's also committed to bolstering the Affordable Care Act, and providing coverage for Medicare recipients. She's less interested in offering new dental and vision benefits in Medicare, as Sen. Bernie Sanders has suggested.
• Addressing climate change is a clear priority for Sinema — putting her on a potential collision course with Manchin.

What we're watching: While Sinema mostly avoids the Sunday talk shows and hallway interviews, she engaged with congressional leaders and the White House all summer, updating her secret spreadsheets on the true cost of programs.

The bottom line: Manchin is looking for a way to get to "yes" on a spending bill, as long as he can stomach the final price tag.

• Sinema has always been slightly more skeptical and has indicated she's comfortable voting no.