One of former Rep. Tom Campbell’s (R) biggest challenges in his newly minted Senate bid is proving he can raise the big money necessary to run a competitive general election campaign against Sen. Barbara Boxer (D) in one of the most expensive states in the country to run political races.

Campbell’s advisers recognize this, but they expressed confidence that he will come out of the gate hard on the fundraising front.

He has six major fundraising events on the calendar in a 30-day span since announcing his switch from the California gubernatorial race to the Senate race on Jan. 14.

Adviser Richard Temple said he believes Campbell will need to raise more than $5 million for the GOP primary — a three-way battle between himself, former Hewlett-Packard CEO Carly Fiorina and state Assemblyman Chuck DeVore.

Fiorina loaned her campaign $2.5 million of her own money in the fourth quarter of 2009, her campaign disclosed earlier this month, and supporters have touted her financial prowess as one of the reasons she would be the best candidate to take on Boxer.

Campbell, meanwhile, has never been known as a fundraising juggernaut — in his 2000 Senate race against Sen. Dianne Feinstein (D), he was outraised $10.5 million to $4.7 million.

Campbell’s campaign is touting a Field poll that shows him leading in the primary race at 30 percent, with 25 percent for Fiorina and 6 percent for DeVore among likely Republican voters. The poll’s margin of error was 7.1 points.