The first night of the Democratic presidential debates drew an estimated 10 million viewers on NBC, according to early numbers first reported by The Hollywood Reporter.

The numbers are based on returns in roughly one-quarter of local Nielsen Media Research markets.

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Final ratings on the debate will be available Thursday afternoon.

The 10 million viewership number only pertains to NBC. MSNBC and Telemundo also simulcasted the debate. Those numbers are also expected Thursday afternoon from Nielsen.

For context, the first Republican debate of the 2016 presidential primary season on Fox News, which featured then-real estate mogul Donald Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE as a front-runner in his first political debate, drew more than 24 million viewers in August 2015.

On the Democratic side in 2015, CNN drew 15.3 million viewers for a debate headlined by former Secretary of State Hillary Clinton Hillary Diane Rodham ClintonFox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio Trump, Biden court Black business owners in final election sprint The power of incumbency: How Trump is using the Oval Office to win reelection MORE, Sen. Bernie Sanders Bernie SandersThe Hill's Campaign Report: Trump faces backlash after not committing to peaceful transition of power Bernie Sanders: 'This is an election between Donald Trump and democracy' The Hill's 12:30 Report: Trump stokes fears over November election outcome MORE (I-Vt.) and three other candidates.

In 2011, the ratings were substantially lower.

For the first GOP primary debate in May 2011, just 3.53 million viewers tuned in to Fox News to see Mitt Romney Willard (Mitt) Mitt RomneyTrump 'no longer angry' at Romney because of Supreme Court stance GOP lawmakers distance themselves from Trump comments on transfer of power McConnell pushes back on Trump: 'There will be an orderly transition' MORE, Herman Cain Herman CainThe Hill's 12:30 Report - Presented by Facebook - Big 10 votes to resume football season Exclusive: Internal documents show officials waved red flags before Trump's Tulsa rally Herman Cain account tweets coronavirus 'not as deadly' as claimed after his death from COVID-19 MORE, Rick Perry Rick PerryEnergy secretary questions consensus that humans cause climate change OVERNIGHT ENERGY: Democrats push resolution to battle climate change, sluggish economy and racial injustice | Senators reach compromise on greenhouse gas amendment stalling energy bill | Trump courts Florida voters with offshore drilling moratorium OVERNIGHT ENERGY: Trump signs major conservation bill into law | Senate votes to confirm Energy's No. 2 official | Trump Jr. expresses opposition to Pebble Mine project MORE and Newt Gingrich Newton (Newt) Leroy GingrichMORE battle it out in the first round of the fight for the party's nomination.

In 2007, the numbers were even lower, with MSNBC drawing just 2.26 million viewers for the first Democratic debate in April 2007.

On the Republican side, only 2.19 million tuned in to ABC for the first GOP debate in August 2007.

The second night of the Democratic debate is slated for Thursday. It will feature former Vice President Joe Biden Joe BidenPelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Hillicon Valley: Subpoenas for Facebook, Google and Twitter on the cards | Wray rebuffs mail-in voting conspiracies | Reps. raise mass surveillance concerns Fox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio MORE and other top-tier candidates including Sanders, South Bend, Ind., Mayor Pete Buttigieg Pete ButtigiegBillionaire who donated to Trump in 2016 donates to Biden The Hill's Morning Report - Sponsored by Facebook - GOP closes ranks to fill SCOTUS vacancy by November Buttigieg stands in as Pence for Harris's debate practice MORE (D) and Sen. Kamala Harris Kamala HarrisHundreds of lawyers from nation's oldest African American sorority join effort to fight voter suppression Biden picks up endorsement from progressive climate group 350 Action 3 reasons why Biden is misreading the politics of court packing MORE (D-Calif.), along with six other hopefuls.