Lew, the current White House Chief of Staff, would replace Timothy Geithner in the role.
Lew's appointment would also mean that Obama would need to find a new chief of staff to replace Lew in his second-term Cabinet. Nichols says that two possibilities for that role are Denis McDonough, a deputy national security adviser, and Ron Klain, who was Vice President Joe Biden’s chief of staff.
It has already been a busy week for Obama's Cabinet reshuffle. On Monday, he nominated former Republican Sen. Chuck Hagel to be the next Secretary of Defense and John Brennan, the White House homeland-security and counterterrorism adviser, to be the new director of the Central Intelligence Agency.
Lew's first order of business will come on the issue of working with Congress to raise the debt ceiling, which needs to happen by the mid-February for the U.S. to continue to be able to borrow money to pay its bills.
Lew is known as a skilled negotiator who played a major role in both the recent deal to avert the fiscal cliff and in negotiating with Republicans in the 2011 debt-ceiling talks.
Geithner has said he plans to leave his post by the end of January, even if the debt-ceiling lift has not been resolved.