With two weeks left in a tight race for the presidency, Donald J. Trump on Tuesday escalated his vicious attacks against Vice President Kamala Harris, making a number of demeaning personal insults at two campaign events.

The onslaught echoed a pattern from his 2016 and 2020 campaigns, when Mr. Trump ramped up his often-wild personal barbs against his opponents as Election Day drew near. He accused Hillary Clinton in 2016 and then-candidate Joseph R. Biden Jr. in 2020 of drug use without a shred of evidence.

But with Mr. Trump facing tight polls and analysts predicting narrow margins in battleground states, the former president’s allies have for months urged him to tone down his personal attacks against Ms. Harris and focus on issues. They have expressed concern that Mr. Trump may risk alienating undecided voters who might be amenable to his political views but turned off by his coarse rhetoric.

Mr. Trump has shown no signs of heeding their guidance and if anything has stepped up the frequency and coarseness of his insults, including using profanity to refer to Ms. Harris on Saturday. Tuesday’s flurry of insults had no swear words, but included a number of swipes that compared the vice president of the United States to an animal and baselessly questioned whether she was a substance abuser.

Though Mr. Trump has for months expressed contempt for Ms. Harris, he had previously reserved his most disparaging language about her for private settings. But as he has become more anxious about her financial edge and as he has struggled to make any single line of criticism against her stand out to voters, he has increasingly fallen back on a variety of wildly false personal attacks as a way to diminish her support.