Donald Trump faces Republican voters for the first time as a convicted felon on Tuesday when the final state nominating contests bring the 2024 US presidential primary to a close.

Trump has already locked up the Republican nomination to run against President Joe Biden, making the votes in Montana, New Jersey, New Mexico and South Dakota formalities.

However, the contests will reflect the mood in the party's grassroots after the former president was found guilty last week of falsifying business records in a conspiracy to unlawfully influence the 2016 election.

Trump claims that the historic verdict has only made him stronger and his campaign reports having received eye-watering levels of donations.

But the turnout and the results in Tuesday's primaries will give a clearer impression of the accuracy of opinion polls in the wake of the verdict that have shown significant numbers of Republicans less likely to vote for him in November.

Poll watchers are also keeping a close eye on Trump's final primary rival Nikki Haley, who is on the ballot in New Mexico.

The former ambassador to the United Nations ended her White House bid in March and recently said she would vote for Trump, but her so-called "zombie" candidacy continues to attract support from a significant minority of Republicans -- possibly in a sign of protest at the frontrunner.

A jury returned guilty verdicts against Trump on Thursday for all 34 charges of falsifying business records to cover up a sex scandal and cheat voters in the final stages of his winning 2016 campaign against Hillary Clinton.

Prosecutors said Trump had sex with porn actress Stormy Daniels soon after his wife Melania had given birth in 2006, and then paid hush money a decade later to avoid the fallout, before creating false paperwork to conceal the payment.

He is due for sentencing on July 11 -- just days before the Republican National Convention in Milwaukee, where he will be officially anointed as the nominee.

Trump faces three other criminal cases, including charges related to his unprecedented attempts to overturn his 2020 election loss to Biden.

Republican donors appear to have rallied behind their standard-bearer.

The Florida billionaire's campaign said Friday it had raised a staggering $53 million in online small-dollar donations in the hours after the verdict was announced -- more than a third from new donors.

However, a tenth of registered Republican voters said Trump's conviction for falsifying business records would make them less likely to support him for president however, in an Ipsos poll that closed on Friday.

In a tight race against Biden, even a small loss of support in his base could hurt Trump significantly.