Spotlight on Jeb Bush in Republican debate
With fewer candidates on stage than any previous Republican debate, the hosts are promising questions focused on policy over personality.
The debate, hosted by Fox Business, could play a key role in the race.
The octet on stage each polled at 2.5% or higher in an average of the four most recent polls.
Those who could not muster the minimum were relegated to the so-called "undercard debate", which was held before the event.
During that debate, the candidates were asked which individual Democrat they most admired - a question they all chose to ignore.
But Rick Santorum, one of the candidates, said that he respected Democrats in general because they were willing to fight for their causes in a way his party is not.
In the main debate, all eyes will be on Mr Bush and on neurosurgeon Ben Carson who has been neck-and-neck with business mogul Donald Trump leading recent polls.
However, in the past few days questions have been asked about parts of Mr Carson's memoir which some allege have been embellished.
The doctor's campaign manager has said that the candidate - the only African American in the race - has prepared an aggressive defence.
Source: BBC News