Donald Trump fired his campaign adviser Sam Nunberg Sunday following allegations Nunberg wrote racist Facebook posts. Earlier in the day, he also took to Twitter and derided his fellow Republican presidential candidates, calling them "puppets" who sought funding and other resources from the Koch brothers. But the billionaire business mogul is still winning the Republican popularity contest, outstripping Jeb Bush, Scott Walker and all other GOP presidential candidates in an NBC News/Wall Street Journal poll published Sunday.

Corey Lewandowski, Trump's campaign manager, announced Sunday Nunberg was "no longer affiliated" with Trump's campaign. Nunberg was accused of writing racist posts on Facebook that were unearthed Friday. Nunberg denied writing them, but Lewandowski told CNN Friday Nunberg would be fired if he had indeed authored posts that used racial epithets and called Obama a "Fascist Nazi Appeaser."

The allegations have not appeared to affect Trump's standing in polls just days before the first Republican debate where participation is limited to the top 10 candidates as determined by an average of the five most recent national polls. 

Nineteen percent of Republican primary voters backed Trump, Sunday’s poll indicated, compared to 15 percent favoring Wisconsin Gov. Scott Walker, 14 percent backing former Florida Gov. Jeb Bush and 10 percent supporting Ben Carson, a retired neurosurgeon. Texas Sen. Ted Cruz took 9 percent, Kentucky Sen. Rand Paul and former Arkansas Gov. Mike Huckabee each took 6 percent and Florida Sen. Marco Rubio got 5 percent.

The first national Republican primetime debate is scheduled for 9 p.m. Thursday. It will be hosted by Fox News, Facebook and the Ohio Republican Party. A separate debate for candidates who do not make the top 10 is scheduled for 5 p.m. that day. Along with the candidates previously mentioned, New Jersey Gov. Chris Christie and Ohio Gov. John Kasich rounded out the top 10 Republican candidates, as ranked by national polling averages, NBC calculated.

Trump tweeted sardonic well wishes early Sunday to his fellow Republican presidential candidates, taking aim at those who sought donations from the billionaire Koch brothers, Charles and David.

Trump was likely referring to a conference in California Saturday organized by the Koch brothers, which Bush, Cruz, Walker and Rubio were scheduled to attend. About 450 conservative donors who have spent nearly $900 million on the 2016 elections so far were present.

Financial statements have shown that Trump is worth $2.9 billion, substantially less than his claims of $10 billion, but still a significant fortune and enough to bankroll a presidential campaign and spare Trump from having to crawl, as he suggested, to donors to fund their presidential ambitions.

Sunday’s NBC News/Wall Street Journal poll surveyed 252 interviewees July 26-30 and had a margin of error of 6.17 percent.