Donald Trump is slumping — and 2 new candidates are surging after the big GOP debate

Donald Trump remains the front-runner for the Republican nomination for president — but two candidates have surged after last week's intense CNN debate.

Trump is slumping in a new CNN/ORC poll released Sunday. He leads the crowded field with 24% of the Republican vote, down 8 points from a similar survey earlier in the month. 

Meanwhile, former Hewlett Packard CEO Carly Fiorina and Sen. Marco Rubio (R-Florida) — whom many pundits identified as the two winners of the debate — have jumped a few spots. Fiorina has vaulted into second behind Trump, grabbing 15% of the vote. She had just 3% support in the previous CNN poll earlier this month.

Rubio is in fourth place with 11% of the Republican vote, also up from 3%. He's also behind retired neurosurgeon Ben Carson, who fell to third place amid Fiorina's rise. Former Florida Gov. Jeb Bush (R) stands in fifth place, with 9% of the vote. He also had 9% in the last CNN poll.

Fiorina has risen from virtual non-existent support to a top-tier candidate with strong performances in the first Republican "undercard" debate in August and in last Wednesday's CNN affair.

Fiorina repeatedly clashed with Trump at the CNN event, including over his recent comments that mocked her face. And she earned perhaps the biggest applause line of the night by advocating for defunding the Planned Parenthood organization.

Indeed, 52% of Republicans who watched the debate said Fiorina did the "best job," according to the CNN poll. She was far ahead of Rubio (14%) and Trump (11%). Meanwhile, 31% said Trump did the "worst job" in the debate, which led the Republican field.

For his part, Rubio downplayed his surge.

"These polls don't really mean anything at this stage, George," he told ABC's George Stephanopoulos on Sunday. "You're a veteran of campaigns. I'm not sure the mid-September winners are where you want to be, obviously. You want to do well, and they're relevant because they're deciding who gets on the stage, but they're not really going to decide this election."

Trump still holds a wide lead on the questions of which candidate Republican voters believe would best handle the economy (with Fiorina in second) and illegal immigration (with Rubio in second). His advantage is smaller on handling foreign policy, as he leads Rubio by a 22-17 margin. Carson, meanwhile, has the advantage over Trump and Fiorina on handling social issues like same-sex marriage.

The CNN poll also revealed a stunning fall for Wisconsin Gov. Scott Walker (R), who was considered one of the early favorites to win the GOP nomination. He received less than one-half of 1% overall, putting him in the same category as candidates who have been relegated to the lower-tier, "undercard" debates.