Sen. Elizabeth WarrenElizabeth Ann WarrenTrump's SEC may negate investors' ability to fight securities fraud Schatz's ignorance of our Anglo-American legal heritage illustrates problem with government Dems ponder gender politics of 2020 nominee MORE (D-Mass.) offered strong support for former Rep. Barney Frank (D-Mass.) to act as interim senator if John KerryJohn Forbes Kerry2020 Dem contenders travel to key primary states When it comes to Colombia, America is in a tough spot 36 people who could challenge Trump in 2020 MORE (D-Mass.) is confirmed as secretary of State, calling him an "extraordinary" option for the seat.

During her mock swearing-in ceremony in Boston on Saturday — mirroring her actual swearing-in on Capitol Hill on Jan. 3 — Warren praised the man she referred to as "my tutor, my guide," according to the Boston Herald.

“There is no one in or out of Washington who has worked harder on financial issues than Barney,” she said. “During the great financial crisis of our lifetime, Barney provided unparalleled insight and extraordinary leadership, resulting in landmark legislation.”

She later told reporters that "if he is appointed to be a senator, I have no doubt that he will be extraordinary."

Her remarks came the day after Frank made it clear on MSNBC that not only does he want the interim appointment, he has been in touch with Gov. Deval Patrick — who was in attendance at the Saturday ceremony — about the seat.

Warren has not weighed in on any of the other possible appointees, which include Victoria Kennedy, the widow of the late Sen. Ted Kennedy (D-Mass.); outgoing Massachusetts Administration and Finance Secretary Jay Gonzalez; and Patrick's outgoing chief of staff, William Cowan.

She also notably declined to endorse a Democratic candidate in the special election, though Rep. Edward MarkeyEdward (Ed) John MarkeyRegulators seek to remove barriers to electric grid storage Markey, Paul want to know if new rules are helping opioid treatment Oil spill tax on oil companies reinstated as part of budget deal MORE (D-Mass.), the only candidate to thus far officially announce he will seek the seat, received the endorsements of a number of prominent Massachusetts and national Democrats, including Kerry himself.

But the high praise for Frank may be a way of paying the congressman back for his help during her campaign; he appeared on the trail multiple times on behalf of Warren throughout her 2012 Senate race.

Patrick has not indicated a preference for an appointee to the seat, saying only during a Friday press conference that “I have a lot of factors I’m considering and [Frank is] definitely on the list.”

The governor has, however, made clear that he'd like to appoint a caretaker, someone who would not run in a special election, and Frank has said multiple times he's not interested in running.

After offering a congratulatory speech during the swearing-in ceremony, Patrick left without speaking to reporters.