Former President Donald J. Trump sharpened his attacks against Vice President Kamala Harris on Friday, accusing her of wanting to impose left-wing values on the nation, painting her as overly liberal on immigration and abortion and calling her a “bum” in a speech to a gathering of religious conservatives.

Speaking at the Believers Summit, a faith-focused conference hosted by the conservative advocacy group Turning Point Action in West Palm Beach, Fla., Mr. Trump invoked the specter of San Francisco — a liberal city long used as shorthand by conservatives eager to denigrate Democrats — as he argued that Ms. Harris would, if elected, impose far-left values on the country.

“Kamala Harris will appoint hundreds of extreme far left judges to forcibly impose crazy San Francisco liberal values on Americans nationwide,” Mr. Trump told the crowd.

Making his second campaign speech since Ms. Harris became the presumptive Democratic nominee this week, Mr. Trump’s barbs seemed more focused than earlier in the week, when he unleashed a flurry of wide-ranging attacks.

Friday’s speech capped off a remarkably tumultuous week in modern political history, and it reflected how Mr. Trump and his campaign have been trying to recalibrate their message after President Biden’s decision on Sunday to end his re-election bid.

Mr. Biden’s move upended a presidential race that Mr. Trump and his team had been anticipating for years. He and his campaign spent considerable time developing sharp attacks on Mr. Biden, and at a rally in North Carolina on Wednesday, much of his speech simply shifted those criticisms to Ms. Harris.