Washington DC - As Democrats rally around the candidacy of Kamala Harris, her rival, Donald Trump, and his Republican surrogates have begun employing significantly more negative and aggressive rhetoric than they had against Joe Biden.

An AFP analysis of the language used in nearly 120 hours of televised speeches and remarks by both parties' candidates and their surrogates from May 1 to September 1 reveals the strategies Republicans have adopted to undermine the Democratic candidate's credibility.

After dismissing President Biden as "crooked," "bad," and "sleepy," Trump and his supporters now mock Harris as a "border czar" for what they say is her badly failed work in curbing undocumented migration to the US.

That nickname has popped up 80 times in rallies – once every 14 times Harris' name is mentioned.

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Republicans have repeatedly accused the vice president of supporting an "open border" policy, which they say allows "millions of illegal aliens" to enter the country.

The negative rhetoric is much more prominent now – 30% more – than it was against Biden before he dropped out of the race on July 21. Trump supporters appearing on television associate her with negative words like "crime," "destroy," "suffer" and "bad."

At the same time, Democrats have been using much more positive, enthusiastic language since Harris succeeded Biden as the party's flag-bearer, with words like "freedom," "joy," "win," and "care" being used 30% more often on talk shows and 70% more in rallies.

Trump and his surrogates have portrayed Harris as far more radical than Biden, applying the labels "left" and "radical" to her twice as often as they did to him.

And since July 21, their use of the term "liberal" in describing Harris has exploded – used eight times more in rallies and six times more in talk shows – while adjectives like "socialist" and "Marxist," rarely applied to Biden, have become commonplace in Republicans' vocabulary.

In the early 1950s, the US went through a "Red Scare" as a strong fear of subversion by far-left elements, including immigrants, hit its peak. But years after the Cold War ended, any hint of communist sympathies remains anathema among US politicians.

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This, presumably, was behind Trump finally settling on "Comrade Kamala" as his favored nickname for his Democratic rival – he has used that term at least 30 times in his rallies.

Through the entirety of Republican remarks analyzed by AFP, "Comrade" and the name of the vice president represent the seventh-most common pairing of words.

The two words most frequently linked, not surprisingly, are "Biden" and "Harris," as Republicans seek to leverage Biden's unpopularity – even after he dropped out of the race. The president's name comes up every five or six times that Harris is mentioned.

By comparison, Democrats are only half as likely to link the names of Biden and their new candidate, and they describe Harris with words such as "leader" and "ready" – ready to be president, that is.

Also among the top 20 terms used to describe her are "fight," "freedom" and "believe" – reflecting the renewed sense of hope that her rapid ascension has brought to the party.