Washington CNN  — 

The race for the Republican nomination for President is more wide open now than perhaps ever before, according to a new Quinnipiac University poll, with five GOP hopefuls all tied with the same amount of support.

Retired neurosurgeon Ben Carson has joined the top tier of Republican aspirants, joining Wisconsin Gov. Scott Walker, Florida Sen. Marco Rubio and former governors Jeb Bush of Florida and Mike Huckabee of Arkansas with 10% of the vote in a national survey released Thursday. In the last Quinnipiac poll – taken before Carson officially joined the race in early May – Carson only captured 3% of the vote.

Surveys of national voters, like Quinnipiac’s, in May 2015 do not speak to how voters in the early states of Iowa or New Hampshire will cast ballots eight months from now. But these national polls have acquired new significance since some media organizations have decided to use the average of recent poll results to determine which, if any, presidential debates the candidates make this summer.

Both Fox News and CNN have said that only the top-10 finishers will earn spots in their premier debates, though CNN will hold a second grouping of candidates who meet the minimum threshold of 1 percent in public polling but are ranked outside the top 10. If based solely on the Quinnipiac poll, the next five contestants to make the top 10, in descending order, would be: Sen. Rand Paul of Kentucky, Sen. Ted Cruz of Texas, real estate mogul Donald Trump, New Jersey Gov. Chris Christie and either Ohio Gov. John Kasich or businesswoman Carly Fiorina, who tie with 2% each.

“Safe to say, the 2016 Republican presidential primary is anyone’s race. With no frontrunner and identical numbers for the top five contenders, it’s a horserace which can only be described as a scrambled field – at least so far,” Tim Malloy, assistant director of the poll, said in a statement.

While Bush, Walker and Rubio have traditionally led most polls, Carson and Huckabee are newer entrants to the field’s top tier. The pair joined the race during the first week of May and their rise may reflect a post-launch bump as much as it does any durable groundswell that will carry them to the GOP nomination.

The Republican candidate will likely face Hillary Clinton in November 2016, who continues to enjoy a huge lead over her Democratic competitors in Thursday’s poll. Her closest competitor, Vermont Sen. Bernie Sanders, who held his first campaign rally this week, trails Clinton by more than 40 points.

Americans, however, still say they do not find Clinton honest or trustworthy, character measures that Republicans see as a liability in a general election.

Yet she still defeats all of her Republican rivals in head-to-head polls, defeating Rubio and Paul by 4 points each. Some Republicans perform much more poorly – Trump loses to Clinton in a hypothetical match-up by 18 points.

Quinnipiac surveyed 1,711 voters nationwide between May 19 and May 26. The margin of error is 2.4 percentage points.