Democratic Sen. Kyrsten Sinema’s views remained a mystery Monday as party leaders eyed votes later this week on their emerging economic legislation and both parties pointed to dueling studies they used to either laud or belittle the measure’s impact.

With Democrats needing all of their 50 votes for the energy and health care measure to move through the Senate, a Sinema spokesperson suggested the Arizona lawmaker would take her time revealing her decision. Hannah Hurley said Sinema was reviewing the bill and “will need to see what comes out of the parliamentarian process.” It could take days for the chamber’s rules umpire to decide whether the measure flouts procedural guidelines and needs changes.

Senate Majority Leader Chuck Schumer, D-N.Y., and Sen. Joe Manchin, D-W.Va., announced an agreement last week on legislation boosting taxes on huge corporations and wealthy individuals, bolstering fossil fuels and climate change efforts and curbing pharmaceutical prices. Overall, it would raise $739 billion over 10 years in revenue and spend $433 billion, leaving over $300 billion to modestly reduce federal deficits.

The legislation would give President Joe Biden a victory on his domestic agenda in the runup to this fall’s congressional elections. If Sinema demands changes, she would face enormous pressure to reach an accord with top Democrats and avoid a campaign-season defeat that would be a jarring blow to her party’s prospects in November.

Manchin is one of Congress’ most conservative and contrarian Democrats. He has spent over a year forcing his party to starkly trim its economic proposals, citing inflation fears, and his compromise with Schumer last week shocked colleagues who’d given up hope that he would agree to such a wide-ranging measure.

Sinema has played a lower-profile but similar role as Manchin — a lawmaker who can be unpredictable and willing to use the leverage all Democrats have in a 50-50 Senate. Last year, she lauded a proposal for a minimum tax on large corporations — which the new legislation has — but has also expressed opposition to increasing corporate or individual tax rates.

“She has a lot in this bill,” Manchin, citing her support for past efforts to rein prices for prescription drugs, told reporters Monday. He said she’s been “very adamant” about not increasing taxes, adding, “I feel the same way.”

Manchin has asserted the bill’s imposition of a 15% minimum tax on corporations earning over $1 billion annually is not a tax increase. He says it closes loopholes such companies use to escape paying the current 21% corporate tax.

Republicans mocked that reasoning and said its tax boosts would weaken the economy and kill jobs. They cited a report from Congress’ nonpartisan Joint Committee on Taxation that said about half of the corporate minimum tax would hit manufacturing firms.

“So in the middle of a supply chain crisis, Democrats want huge job-killing tax hikes that will disproportionately crush American manufacturing and manufacturing jobs,” said Senate Minority Leader Mitch McConnell, R-Ky.

Biden has said he will not raise taxes on people earning under $400,000 annually. Manchin has said the Democratic package honors that pledge.

Republicans recently distributed another Joint Committee on Taxation analysis that said the measure would raise taxes on people earning below that figure. Democrats criticized the study as incomplete, saying it omitted the impact on middle-class families of the bill’s health insurance subsidies and clean energy tax cuts.

Democrats touted a report by Mark Zandi, chief economist at Moody’s Analytics. It said the measure “will nudge the economy and inflation in the right direction, while meaningfully addressing climate change and reducing the government’s budget deficits.”

Schumer said he expected votes to begin this week in the Senate, where Vice President Kamala Harris could cast the tie-breaking vote to assure its passage. The narrowly divided House has left town for an August recess, but Democratic leaders have said they would bring lawmakers back for a vote, perhaps next week.