SAN FRANCISCO — US Senator Bernie Sanders on Sunday called on California Democrats to unite against Donald Trump, kicking the 2020 presidential campaign into high gear with jabs against the Republican president and a veiled swipe at Democratic rival Joe Biden.

Sanders called Trump "a racist, a sexist, a homophobe and a religious bigot" in a speech capping off a state Democratic convention that drew fourteen of the 24 candidates to make their case before 5,000 delegates, guests and press in the most populous — and most heavily Democratic — US state.

"Together we are going to defeat a president who has the most corrupt administration in history," Sanders said, "and a president who knows nothing about real American values."

The San Francisco convention became a window into the forces at work in the Democratic Party as it seeks to recover from Trump's populist-fueled victory in 2016.

The party's left-leaning delegates greeted Sanders and liberal US Senator Elizabeth Warren like rock stars.

Former Colorado Governor John Hickenlooper drew boos when he said socialist policies would not propel the party to victory, and other moderates were booed for rejecting the idea of a universal public health care system, or Medicare for All.

Former Vice President Joe Biden, who leads Sanders in polls for the Democratic nomination in California and nationwide, did not attend the convention, drawing barely veiled criticism from Sanders.

Sanders noted that the fourteen candidates who addressed the convention, as well as some who had "chosen for whatever reason not to be in this room," offer a variety of ways to approach a campaign against Trump. But Sanders rejected the centrist approach favored by Biden and some other candidates.

On issues like health care, pharmaceutical prices and climate change wracking the country, "there is no middle ground," Sanders said.

Addressing concerns among some Democrats that a moderate would be more electable than a fiery progressive, Sanders said such an approach would not generate the enthusiasm needed to defeat Trump.

"We will not defeat Donald Trump unless we bring excitement and energy into the campaign and unless we give millions of working people and young people a reason to vote and a reason to believe that politics is relevant to their lives," Sanders said.

California, which will send nearly 500 delegates to the party's nominating convention next year, took on new heft for the 2020 campaign after moving its nominating election to March from June. Democrats hold all statewide elective offices in the state, and dominate both houses of the legislature.

US Senator Kamala Harris, a native daughter who has been eclipsed in early polling in California by Biden and Sanders, made clear she was not taking her home state for granted.

On Saturday, supporters with signs bearing her name and shouting "Kamala! Kamala!" formed a gauntlet that Sanders was forced to walk through on his way into a labor union breakfast.

"I am here to earn everyone’s support, and I’m going to fight to earn it," Harris said at a breakfast held by the party's women's caucus. — Reuters