The US presidential race remains neck-and-neck according to polls released Sunday, two days before Kamala Harris and Donald Trump hold their first -- and potentially only -- televised debate.

The latest polling confirms that Trump retains locked-in support from about half of voters, despite the Republican's historic status as a convicted felon and his role in instigating the unprecedented attempt to overturn his 2020 loss to Joe Biden.

Harris, who only jumped into the race after President Biden quit in July, has rapidly transformed herself from a little-noticed vice president into a serious contender. However, the polls show she has not made a major breakthrough, leaving the race a toss-up.

A New York Times/Siena poll found that 78-year-old Trump is leading Harris nationally by 48 to 47 percent, well within the margin of error.

US presidential elections are decided by tallying the results of state-by-state contests, rather than an overall national popular vote, meaning that a tiny handful of swing states typically determine the balance.

The poll found Harris, 59, narrowly ahead in Wisconsin, Michigan and Pennsylvania, and tied in four other swing states: Nevada, Georgia, North Carolina and Arizona.

A CBS News/YouGov poll put Harris ahead by one percentage point in Michigan and Wisconsin and tied in Pennsylvania.

The election is already chaotic, with 81-year-old Biden dropping out amid concerns over his age, Trump narrowly surviving an assassin's bullet at a rally, and fears mounting that Trump will again refuse to concede if he loses in November.

However, the latest numbers confirm that each candidate retains a remarkably stable base of loyalists, almost evenly splitting the country.

One game changer could be Tuesday's ABC News debate, the only one scheduled between the two.

Trump will be under pressure to rein in his characteristic use of insults and intimidation as he stands next to a mixed-race candidate vying to become the first female president in US history.

Harris will need to use the huge viewership to connect with Americans in a way that she was unable to as vice president and has had little time to accomplish in her super-condensed campaign run.

With Trump now the oldest presidential nominee in US history, she is pitching an optimistic, forward-looking message in contrast to Trump's apocalyptic claims that the country faces terminal decline without him in the White House.

But Harris has also been accused of running on vague optimism and unity at the expense of putting out concrete policies.

She finally addressed the growing pressure late Sunday when her campaign put out a policy page, touching on subjects from unions and cost-of-living issues to health care.

- Sexist taunts -

At the same time, Harris will have to solve the conundrum of how to debate Trump, who habitually makes false statements on nearly every topic and loves to get under his opponents' skin. Biden, in his only debate against Trump before dropping his candidacy, found himself entirely unable to cope.

Already, Trump has been subjecting Harris in his speeches to racist and sexist taunts, deliberately mispronouncing her name and calling her "crazy" and a "Marxist."

"It will take almost superhuman focus and discipline to deal with Donald Trump in a debate," Harris supporter and current transportation secretary Pete Buttigieg told CNN.

The Harris campaign announced it would "barnstorm battleground states" after the debate, beginning in North Carolina, then Pennsylvania.

Trump held a rally in Wisconsin on Saturday where he appealed to his mostly white, working-class base with a dark speech claiming that he is struggling against a "rogue regime" where Democrats "imported murderers, child predators and serial rapists from all over the planet."

On his Truth Social platform, he warned that once back in the White House he would impose "long prison sentences" on all those he said were planning "cheating" in November.