Following a trio of Republican campaign announcements last week, Ben Carson leaps to the top spot of GOP presidential candidates in the latest Fox News poll tied with presumed GOP front-runner Jeb Bush.

Carson, former Hewlett-Packard CEO Carly Fiorina and former Arkansas Gov. Mike Huckabee all entered the race for the Republican nomination early last week, but none has seen as dramatic a bump as the retired neurosurgeon.

Both Bush and Carson sit atop the Fox poll at 13 percent each among Republican primary voters. That's a seven-point bounce for Carson who was at just 6 percent in the same poll in April.

The poll comes amid Bush's shifting statements on whether he would have authorized the Iraq War. Being tied to the unpopular war, launched by his older brother President George. W. Bush, would be a potential liability to the former Florida governor's yet-to-be-launched bid for the Oval Office.

This issue, however, likely had little impact on the Fox poll, which wrapped its surveying of respondents Tuesday, just a day after his interview with Fox's Megyn Kelly, in which he said he would have authorized the war even knowing what we know now. He reversed that stance Thursday.

Carson is largely unknown among all respondents – 49 percent said they had "never heard of" the retired pediatric neurosurgeon. Still, he was viewed more favorably than not among those who had heard of him by a 26 to 16 percent margin.

Meanwhile, it's the opposite for Bush. Only 9 percent had never heard of him, but he's viewed more negatively than positively by a 44 to 37 percent margin.

Fiorina and Ohio Gov. John Kasich were even less known among all voters with 58 percent saying they did not know or were unsure of Fiorina and 63 percent saying so of Kasich. Kasich has yet to announce whether he will make a run for the White House in 2016.

Rounding out the top five presidential nominees likely Republican primary voters would endorse were Wisconsin Gov. Scott Walker (11 percent), Huckabee (10 percent) and Florida Sen. Marco Rubio (9 percent). Of this group, only Walker has not officially gotten in the race, but it is widely anticipated he will. Of those surveyed, 46 percent say they have not heard of Scott Walker.

Huckabee was the top second-choice pick for Republican voters (11 percent) followed by Bush, Paul and Cruz (all with 10 percent).

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