Senate Democrats want to require President-elect Donald Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE's Cabinet picks to release their tax returns as part of the confirmation process.

Democratic Sens. Debbie Stabenow Deborah (Debbie) Ann StabenowOVERNIGHT ENERGY: Trump rollbacks could add 1.8 billion tons of greenhouse gas emissions over 15 years: analysis | Intensifying natural disasters do little to move needle on climate efforts | Experts warn wildfire smoke could worsen COVID-19 GAO report finds brokers offered false info on coverage for pre-existing conditions Democrats back away from quick reversal of Trump tax cuts MORE (Mich.), Patty Murray Patricia (Patty) Lynn MurraySenate Democrats introduce legislation to probe politicization of pandemic response Trump health officials grilled over reports of politics in COVID-19 response CDC director pushes back on Caputo claim of 'resistance unit' at agency MORE (Wash.) and Ron Wyden Ronald (Ron) Lee WydenGOP set to release controversial Biden report Democrats fear Russia interference could spoil bid to retake Senate GOP senator blocks Schumer resolution aimed at Biden probe as tensions run high MORE (Ore.) said Thursday they want to change Senate rules in January to require Cabinet and other "senior" nominees to hand over the past three years of their tax returns.

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"If [Trump's] going to nominate billionaires with so many potential conflicts of interests...we want to be able to scrutinize them even more than usual," Murray, who will be the No. 3 Senate Democrat next year, told reporters.

Murray added that the extra security is needed because of Trump's "secrecy and cronyism."

The Democrats argue that under current rules, only three committees — Finance, Budget and Homeland Security and Governmental Affairs — have explicit authority to force a nominee to hand over their tax returns.

Democrats have focused on Trump's tax returns for months, arguing the president-elect is breaking decades of precedent by not releasing them.

The real state mogul said during the campaign that he couldn't release the documents because of an IRS audit, though the agency said it wouldn't prevent him from disclosing the information.

Wyden introduced legislation this year to require presidential nominees to disclose their tax returns, though that proposal stalled in a GOP-controlled Congress.

"With the president-elect flouting a 40-year bipartisan tradition ... we think it's more important than ever to ensure that senior officials across government aren't operating under a different tax code than everyone else," he added Thursday.

Wyden is planning to reintroduce a modified version of his bill next year.

Democrats have panned many of Trump's cabinet nominees, pledging to give them "thorough" hearings though the picks will only need a simple majority clear the upper chamber.

Republicans are expected to have a 52-seat majority next year.

Trump has tapped a number of top Wall Street executives to fill his ranks, sparking criticism from Democrats.

Steven Mnuchin, a former Goldman Sachs trader and now hedge fund manager, has been tapped for Treasury Secretary, and billionaire investor Wilbur Ross for Commerce secretary.

Murray added that while Trump pledged to "drain the swamp," "he seems to think the way to do that is by filling it with even bigger swamp creatures."