SACRAMENTO, Calif. — California GOP Senate challenger Carly Fiorina was admitted to a hospital Tuesday to be treated for an infection associated with her reconstructive surgery after breast cancer.

The former Hewlett-Packard Co. chief executive is being treated with antibiotics, Deborah Bowker, the campaign's chief of staff, said in a statement.

Scheduled campaign events in Riverside and Coachella were canceled. The campaign did not say which hospital Fiorina was being treated; she had undergone surgery for her breast cancer at Stanford Hospital.

"While this will impact her campaign schedule today, Carly is upbeat and her doctors expect her to make a quick and full recovery and be back out on the campaign trail soon," Bowker said in the statement.

Boxer's campaign sent their well wishes.

"We wish Carly Fiorina a speedy recovery and hope she is able to return to her normal schedule soon," Boxer campaign manager Rose Kapolczynski said in a statement.

Fiorina, 56, was diagnosed with breast cancer in February 2009 before she formally announced her run for the seat of Democratic Sen. Barbara Boxer. She completed chemotherapy and radiation treatments a year ago and had reconstructive surgery in July after having a double mastectomy.

The first-time candidate has maintained a busy campaign schedule in the final weeks of the race, traveling throughout a state that is big enough to stretch from Maine to North Carolina. On Tuesday, she was scheduled to meet with small business owners in the two Riverside County cities to discuss jobs and the economy.

Boxer is scheduled to appear later in the day with first lady Michelle Obama in Los Angeles. President Barack Obama campaigned for the senator at a rally at the University of Southern California on Friday.

Recent polls show the race between the two women tightening.

A University of Southern California-Los Angeles Times poll released Sunday showed Boxer maintaining a narrow advantage, 47 percent to 41 percent, against Fiorina. The gap was smaller than the same poll showed a month ago.

Last week, Fiorina pumped another $1 million of her personal fortune into her campaign for the final stretch.