The usual California's governor, Gov. Jerry Brown, is away on business for a trade mission to Mexico.
In his absence, the position moved to Lieutenant Governor Gavin Newsom but he was required to attend a Special Olympics event on the East Coast.
The next acting governor, Senate President pro tempore Darrell Steinberg, is scheduled to leave the state for Chicago today.
As Gov. Brown is not due to return from Mexico until this evening, Speaker Atkins is due to hold the office in the estimated eight or nine hours between Mr Steinberg’s departure and Gov. Brown’s return to the state.
In doing so, she becomes California’s first lesbian governor.
In 2005, Ms Atkins became the first lesbian Mayor of San Diego, and in May 2014 succeeded John Pérez, the first gay Speaker of the California State Assembly, to become the first lesbian holder of the office.
Atkins kissing her spouse, Jennifer LeSar,
on the day she was sworn in as Assembly speaker