Republican presidential candidates will meet in debate on Wednesday -- again snubbed by clear frontrunner Donald Trump -- as the party's increasingly hardline position on abortion faces scrutiny after disappointing state elections results a day earlier.

The ex-president will skip the Miami event and instead hold a rally 11 miles (18 kilometers) away, maintaining his strategy of refusing to debate challengers.

The five remaining hopefuls have little prospect for meaningful breakthroughs against the populist leader of the hard-right Make America Great Again movement -- even though Trump faces multiple criminal indictments and will spend much of the next year ahead of the 2024 election in courtrooms.

The main also-rans to watch remain Florida Governor Ron DeSantis and Trump's former UN ambassador Nikki Haley.

DeSantis is struggling after an initially brisk start to his campaign to become the new face of the Republican Party -- casting himself as an equally hard-right but much more youthful, and scandal-free, version of 77-year-old Trump.

He now lags behind Trump by nearly 45 percentage points, according to polling aggregator RealClearPolitics.

Haley, who has benefited from DeSantis's decline and promotes a more centrist view on abortion, has a solid third place behind Trump and the Florida governor.

Also on stage will be entrepreneur Vivek Ramaswamy, Senator Tim Scott and former New Jersey governor Chris Christie, who stands out as the only pretender to the Republican crown willing to mount harsh attacks on Trump.

- Abortion issue key -

Abortion could be a key debate topic after Tuesday's elections where voters demonstrated the unpopularity of harsh Republican restrictions.

In Republican-led Ohio, voters passed a referendum enshrining the right to an abortion in the state constitution.

Reproductive rights were also in the spotlight in conservative-leaning Kentucky, with the southern state re-electing incumbent Democratic Governor Andy Beshear after he campaigned on protecting abortion rights from the Republican legislature.

In Virginia, Democrats won control of the state assembly, dashing a much-hyped campaign led by Republican Governor Glenn Youngkin to use a victory in the legislative races to enact a ban on abortions after 15 weeks of pregnancy.

The defeat for Youngkin and his party also ended speculation that the governor might use a dramatic election victory on Tuesday to power his own late entry into the presidential race as a more moderate alternative to Trump.

The Republican primaries will kick off January 15 in the midwest state of Iowa, where DeSantis recently won the governor's prized endorsement, sparking vocal outrage from Trump.

The eventual nominee is to face off against President Joe Biden in next November's presidential election.

The previous two Republican debates have been noisy, but not exactly eventful affairs -- particularly since they lacked the media star power of Trump.

With fewer candidates making the stage this time, Ramaswamy, polling in fourth place, told AFP he was "hopeful the debate will be more productive."

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