Republican presidential candidates seeking to make the second debate stage in September will face tougher criteria for doing so, according to a person familiar with the new rules.

To make the next debate, which will be held on September 27 at the Ronald Reagan Presidential Library in Simi Valley, California, Republican presidential candidates will need at least 3% in two national polls or in one national poll and two polls from separate early-voting states -- Iowa, New Hampshire, South Carolina or Nevada.

Qualifying polls must be conducted on or after August 1 and meet several requirements, including that they've surveyed at least 800 "registered likely Republican voters" and are not conducted by a company affiliated with a candidate.

Candidates must also have a minimum of 50,000 unique donors, with at least 200 donors in 20 states or territories.

The new rules were first reported by Politico.

Both of these metrics are increases from the requirements to make the first debate stage in Milwaukee later this month, where candidates need to reach 1% in three national polls, or 1% in two national and two early state polls, as well as collect 40,000 unique donors.

By CNN's tally, eight candidates have met the polling threshold for inclusion in the August debate: Former President Donald Trump, Florida Gov. Ron DeSantis, tech entrepreneur Vivek Ramaswamy, former Vice President Mike Pence, former South Carolina Gov. Nikki Haley, South Carolina Sen. Tim Scott, former New Jersey Gov. Chris Christie and North Dakota Gov. Doug Burgum.

Seven of them say they've also met the fundraising requirements for August: Trump, DeSantis, Scott, Haley, Christie, Ramaswamy and Burgum. Pence is the only candidate who has met the polling threshold but has not yet claimed to have reached the fundraising criteria.

In order to qualify for either debate, candidates also need to sign a pledge committing to supporting the eventual Republican nominee.