Billionaire Donald Trump remains in first place in the race to win the Republican presidential nomination for 2016, but his support has fallen to 24 percent from 32 percent previously, a CNN/ORC poll released on Sunday shows.

Former Hewlett-Packard chief executive Carly Fiorina, considered to have performed well in a CNN-sponsored debate of Republican candidates on Wednesday, shot up to second place with 15 percent from only 3 percent in early September, the poll showed.

The poll was conducted among 1,006 Americans from Sept. 17 to 19, and had a margin of error of plus or minus 3 percentage points.