Last week, candidates were complaining about their not being included in some debates. This week, low attendance is forcing National Public Radio to cancel its forum with the Republican candidates in Columbia, S.C.

“We had commitments, we had some people whose schedules were fluid, and the ultimate decision was to cancel it,” said Andi Sporkin, a spokeswoman for NPR.

The debate, scheduled for next Wednesday, would have come one day after the Michigan primary, which is shaping up to be a pivotal race for the Republicans. South Carolina’s Republican primary will be on Jan. 19. It is not the first political gathering to be canceled or postponed this season. When the top-tier contenders declined to attend his Republican forum on public television in September, the host, Tavis Smiley, held the event anyway, with the absent candidates’ names on lonely lecterns.