President Barack Obama will raise campaign cash next week for Sen. Barbara Boxer (D-Calif.) and Democrats' Senate campaign committee.

Obama will help raise funds for Boxer for the second time in a month and a half with a fundraiser in San Francisco. The president will also hold a separate fundraiser for the Democratic Senatorial Campaign Committee (DSCC).

The president last stopped in Los Angeles in late April, when a set of fundraiser brought in $3.5 million in funds for Boxer and the Democratic National Committee (DNC).

Boxer is facing one of her toughest reelection challenges this year, with a number of Republican candidates -- most notably former Hewlett-Packard CEO Carly Fiorina, state Assemblyman Chuck DeVore, and former Rep. Tom Campbell -- vying to unseat her.

California's major cities are some of the largest media markets in the country, making campaigns there some of the most expensive statewide races to organize.