Kamala Harris crisscrosses Michigan on Monday while Donald Trump heads to Georgia -- another of the decisive swing states in one of the closest US elections in history -- after presiding over a dark mega-rally aimed at whipping up his right-wing base.

With only a week until November 5 Election Day, early voting has already seen more than 41 million Americans cast ballots -- joined by outgoing Democratic President Joe Biden on Monday, who will vote in his hometown Wilmington, Delaware.

Tensions are soaring in a race that polls show too close to call, fueled by fears that Trump will again refuse to recognize a defeat, as he did in 2020. The Republican continues to claim he was cheated, and his rhetoric has become increasingly infused with violence and threats.

Outrage erupted across the political spectrum when one of the warm-up speakers at Trump's Sunday rally in New York's Madison Square Garden likened majority-Hispanic Puerto Rico to "a floating island of garbage."

The Trump campaign went into a rare bit of damage control, saying this "does not reflect the views of President Trump."

However, comedian Tony Hinchcliffe was unrepentant, writing on social media that his critics "have no sense of humor" -- a comment reposted by Trump's son and advisor Don Trump Jr.

Harris, 60, called Trump "increasingly unstable and unhinged" in an interview with CBS News and goaded the 78-year-old to undergo a cognitive test, saying she would "take the same one."

As the clock ticks down, the challenge for Harris and Trump is both to energize core supporters and pull in the tiny number of persuadable voters who might still tip the balance -- especially in the seven swing states where polls show them running neck-and-neck.

Harris, who spent Sunday in must-win Pennsylvania, will hold three events in Michigan, while Trump will hold two in Georgia -- a pattern set to be repeated around the country's other battlegrounds for the next seven days.

On Tuesday in Washington, Harris will deliver what her campaign calls a "closing argument," in a nod to her career as a federal prosecutor.

The Democrat will speak from the same spot on the Mall near the White House where then president Trump stoked his supporters on January 6, 2021, to launch a violent assault on Congress in an attempt to stop certification of his reelection loss to Biden.

Trump -- the oldest presidential nominee ever and also the first to have been convicted of crimes -- used a packed Madison Square Garden for his own closing pitch on Sunday.

The campaign celebrated the event in the legendary arena as a show of force and energy, claiming that tens of thousands of supporters thronged outside in addition to the capacity crowd inside.

- 'JOY'? -

"PURE JOY," posted senior Trump immigration advisor Stephen Miller on X.

But much of the event -- likened by Democrats to an infamous 1939 rally of American fascists in the same venue -- was not joyous.

Trump lashed out at the "enemy from within," which he described as an "amorphous group" that includes the Democratic Party leadership.

And his allies unleashed crude, sometimes openly racist rhetoric to mock Harris sexually, make fun of Hispanics' birth control, parody Jews and Palestinians, and poke fun at a Black man by referring to a watermelon -- a deep-rooted racist stereotype in the United States.

"RACIST RALLY" read the front page headline on the New York Daily News tabloid.

The row over the comedian's crude joke came as Puerto Rican superstar rapper Bad Bunny endorsed Harris.

Residents in the US territory cannot vote in presidential elections, but those within the United States proper -- which includes about 450,000 Puerto Ricans in Pennsylvania -- can.

Hanging over the entire election is concern that the aftermath will be as chaotic -- and perilous -- as in 2020. According to a CNN poll out Monday, only 30 percent of Americans think Trump would concede defeat, while 73 percent think Harris would accept a loss.