Two-man race for Rep nom - Cain to endorse Romney or Gingrich

With the implosion of Herman Cain's campaign amid accusations of adultery and sexual harassment, the once-crowded 2012 United States Republican presidential field appears to be narrowing to a two-man race between Mitt Romney and Newt Gingrich.

GOP voters have one month before the lead-off Iowa caucuses.

Gingrich is showing strength in the latest Iowa poll, while Romney is strong in New Hampshire, site of the first primary.

Romney has maintained a political network since his failed 2008 presidential bid, especially in New Hampshire.

Gingrich, whose campaign nearly collapsed several months ago, is relying on his debate performances and the goodwill he built up with some conservatives as a congressional leader in the 1980s and 1990s.

Cain's suspension of his campaign Saturday, and Texas Governor Rick Perry's continued struggles to make headway with voters, have focused the party's attention on Romney, a former Massachusetts governor, and Gingrich, a one-time congressman from Georgia.

They offer striking contrasts in personality, government experience and campaign organisation.

Their political philosophies and differences are a bit harder to discern.

Both men have changed their positions on issues such as climate change. And Gingrich, in particular, is known to veer into unusual territories, such as child-labour practices.

Cain's once-prospering campaign was undone by numerous allegations of sexual wrongdoing.

Gingrich, twice divorced and now married to a woman with whom he had an extramarital affair, has been the most obvious beneficiary of Cain's precipitous slide.