Washington (CNN) -- A federal judge from Montana and the dean of Harvard's law school are among several names being added to the short list of potential nominees to the U.S. Supreme Court, a government source said.
Sidney Thomas, a 14-year veteran on the U.S. Court of Appeals for the 9th Circuit, is being vetted by the White House, said the source, who has been regularly consulted in the selection process.
Two women who were not on other published lists of potential candidates are now being seriously considered.
Harvard Law school dean Martha Minow has been on the school's faculty since 1981. And Elizabeth Warren heads the Congressional Oversight Panel, which reviews government efforts to boost the shaky financial and private investment sector. Neither woman has judicial experience.
Sources close to the selection process said the new names represent an effort to expand what had been a short list of candidates, many of them left over after last year's court vacancy was filled by Justice Sonia Sotomayor.
Some White House officials have been urging the president to expand the list of possibles to include more non-judges and people with different backgrounds and from other regions of the country. All the current justices except the retiring John Paul Stevens are Ivy League law school graduates.
Thomas, who is white, was born in Bozeman, Montana, in 1953. He is little-known and has attracted little fanfare beyond the San Francisco, California-based court, which is considered the most liberal among the nation's 13 appeals courts.
Among rulings he authored was a 2006 decision in Nadarajah v. Gonzalez, in which Thomas concluded that the government illegally detained Ahilan Nadarajah for four years while the Justice Department appealed a grant of asylum. The man is a member of the Tamil ethnic minority and asserted that he was tortured and persecuted by members of the Sinhalese majority.
Minow is the daughter of former Federal Communications Commission head Newt Minow. She clerked for former Justice Thurgood Marshall. In her mid-50s, Minow replaced as dean the woman considered near the top of potential high court nominees, Elena Kagan, now solicitor general.
Warren is also a Harvard law professor. She has been a regular on the talk-show circuit, including CNN, to discuss the economy's effect on families. The Oklahoma native has also co-authored two books with her daughter.
One name mentioned by some analysts for years as a potential blockbuster choice has been all but ruled out for consideration.
Supporters of Hillary Clinton have long touted her credentials, but White House spokesman Tommy Vietor said Monday that the president "thinks Secretary Clinton is doing an excellent job as secretary of state and wants her to remain in that position."
The White House has given no indication when Obama will name a successor to Stevens, who announced Friday that he will retire this year. Stevens has been on the high court nearly 35 years and leads the four-justice liberal bloc.