BURLINGAME – Rival GOP presidential campaigns weren't the only ones trying to shore up support at this weekend's California Republican Party convention.

A handful of could-be challengers to U.S. Democratic Sen. Dianne Feinstein stormed the gathering with campaign signs, volunteers and speeches at caucus meetings.

Elizabeth Emken, Dan Hughes, Al Ramirez and Greg Conlon aren't exactly household names – even among Republican activists at the convention. Party leaders' efforts to recruit a so-called "top tier" challenger, such as a sitting member of Congress or someone with personal wealth to pour into a campaign, were unsuccessful.

But the candidates said they believe Feinstein, long a popular public figure and formidable opponent in Democrat-dominated California, can be had. Polls showing a drop in Feinstein's approval rating and voter disappointment with the status quo in Washington, D.C., creates an opportunity for an upset, they said.

Republicans acknowledge that raising the cash needed to run statewide is a major challenge. One GOP consultant said the relative newcomers would need at least $10 million just to make their names known to California voters.

"They come to a convention like this to press the flesh and to meet people, but I think the reality is whether or not they're going to be considered serious contenders is going to depend on their ability to put some money in the bank," said Jon Fleischman, who has written about both Emken and Hughes on his blog, www.FlashReport.org.

Feinstein's campaign said the current crop of Republicans' lack of name identification and meager fundraising – Emken took in just $39,000 in 2011 and ended the year in debt, and Hughes' $100,000 included $50,000 from his own pocket – present little threat to the prominent Democrat and her multimillion dollar campaign war chest.

"If this race plays out as a bunch of unknowns who have no serious funding, Orly Taitz will probably win the primary," said Feinstein adviser Bill Carrick, referring to the so-called "birther" activist who said last year she might enter the race.

For Emken, a goal of the weekend was to break out of the field of nearly a dozen possible GOP candidates as a clear front-runner. Her campaign team, which includes a former California Republican Party spokesman and veterans of Carly Fiorina's 2010 Senate run, pointed to endorsements from former Secretary of State Bill Jones, National Tax Limitation Committee President Lew Uhler and past state party Chairman Ron Nehring.

"I think we're ready for someone who's real, and I'm real," the Danville Republican said in an interview, adding, "To be frank with you, I'm it. There's no one else with a statewide team. There's no one else that's put together a real campaign."

The longtime advocate for autism research, who lost a primary bid for Congress in 2010, was greeted by a crowd of young volunteers organized by her campaign as she entered the Hyatt Regency Saturday. They chanted "Emken! Emken!" as they escorted her to a caucus meeting.

Hughes, an Oceanside Republican who runs a Carlsbad business that provides ventilation services to hospitals throughout the state, is a first-time candidate and a newcomer to the state party convention scene. He said voters will be drawn to him once they see he has been a "passionate conservative my entire life."

He scored the endorsement of former state Assemblyman Chuck DeVore, the tea party's top candidate in the 2010 U.S. Senate primary, heading into the convention.

"We need an articulate person with the strong moral and principle-centered foundation, the leadership, depth of experience to carry our message, the message of our conservative values," Hughes said.

Los Angeles businessman Ramirez and 2002 state treasurer candidate Conlon, a CPA who has run for the Assembly and Congress in recent elections, also distributed campaign materials and posted signs throughout the hotel.

But with delegates and party leaders focused on the presidential race and defeating President Barack Obama, stage time and attention from attendees were hard to come by.

Emken had drafted a speech for one of the keynote events, though her campaign said nothing official had been finalized. She didn't make the cut for Saturday's lunch and dinner events, which featured presidential candidate Newt Gingrich, former candidates Herman Cain and Tim Pawlenty, and talk-radio host Michael Reagan. A reception held by Hughes on the second floor of the Hyatt Regency atrium appeared to be sparsely attended Saturday evening.

As the weekend came to a close, several delegates said they were still far from decided on a favorite candidate.

Carl Brickey, who saw several of the candidates speak, said Emken and Hughes came across as "credible candidates who can stand next to (Feinstein) and present a Republican platform or vision."

But the Elk Grove Republican said the party did not give the candidates enough exposure at the event, and acknowledged that he didn't expect to be quick to decide a favorite.

"There are so many of them … for me, as somebody who's not familiar with them, it's going to take awhile for me to go through all of those candidates and see who they are, where they stand, and which one I am going to be supporting," he said.

The Senate hopefuls said they're ready to put in the work it takes to win.

"It's a David and Goliath here," Hughes said. "I'm not kidding myself."

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