President Obama steps off Air Force One upon arrival at Los Angeles International Airport in Los Angeles, where he was to  attend a series of fundraisers and address the U.S. Conference on Mayors. (AFP/Getty)

BEVERLY HILLS, Calif. — President Obama wrapped up a day he began with an angry and frustrated reaction to the mass killings in Charleston, S.C., by acknowledging that he has been unable to change the culture of polarization and gridlock in Washington.

But he also challenged Democratic supporters to do their part to make the political changes rather than remain disillusioned about the inability of the nation's capital to respond to gun violence and other problems.

"When I ran in 2008, I in fact did not say I would fix it. I said we could fix it," Obama told an audience of about 250 at a fundraising event here at the stately hillside home of film mogul Tyler Perry. "I didn't say, 'Yes, I can.' I said, 'Yes, we can.'"

The president continued: "If you’re dissatisfied that every few months we have a mass shooting in this country killing innocent people, then I need you to mobilize and organize a constituency that says this is not normal and we are going to change it."

Obama arrived here Thursday afternoon to kick off a four-day California trip during which he will attend four Democratic fundraisers in Los Angeles and San Francisco, speak to the U.S. Conference of Mayors and play golf in Palm Springs.

During his appearance at the fundraiser at Perry's house — which was to raise money for the Democratic National Committee — Obama was aiming to rally his audience ahead of the 2016 presidential election cycle. He cited accomplishment, including improvements in the economy, but the tragedy in Charleston could not be avoided.

In addressing the tragedy, Obama sounded notes of frustration about the state of Washington's dysfunction, and he cited a letter he received from a man in Colorado who had voted for him twice but expressed disillusionment over the continuing gridlock.

"On that issue, I had to tell him, 'You're right,'" Obama said. "I am frustrated. You have every right to be frustrated because Congress doesn’t work the way it should. Issues are left unattended. Folks are more interested in scoring political points than getting things done."

He added that "incentives are built into the system that reward the short term, reward a polarized politics, reward being simplistic instead of being true, reward division. As mightily as I have struggled against that, I told him, 'You’re right. It still is broken.'"