"I don't expect there to be any reason why he should not be confirmed this time around as well," Baucus said.
The senator urged his fellow members to treat Lew with respect, but did not discourage them from asking "tough questions" of Lew.
"I certainly will," he added.
Sen. Orrin Hatch (R-Utah) argued that Lew's time at the bank, which received bailout assistance during the financial crisis, needs to be properly probed if he is to take the helm of the Treasury Department.
"If taxpayers are going to prop up failed banks, they have a right to know what a key executive like Mr. Lew did at that time," he said. "The American people will want to know what his role was there and how that might have prepared him for this critical job after the most severe financial crisis and prolonged economic downturn in generations."
Hatch added that if Lew's Citigroup stint is supposed to bolster his bona fides on financial markets, then his "tenure and financial compensation" there are fair game as well.
Lew is expected to be pressed by GOP lawmakers on $56,000 he invested while working at Citigroup in a fund that was based in the Cayman Islands, in the infamous Ugland House that provides tax shelter to thousands of corporate entities.
Sen. Chuck Grassley (R-Iowa) vowed to press Lew on the investment when he appears before the panel, noting that Obama had previously been "almost obsessively critical of offshore investments."
Lew sold the investment at a loss upon becoming head of the Office of Management and Budget in 2010.
The White House has defended Lew, saying the investment was disclosed — as it was during previous nominations — and he had no role in creating or managing the fund.
Hank Paulson, who served as President George W. Bush's Treasury secretary after heading Goldman Sachs, also had numerous investments in the Cayman Islands when he came up for confirmation.
This post updated at 4:37 pm.