BOSTON — Donald Trump is maintaining a commanding 2-1 lead in the latest poll of GOP caucus goers in Iowa, and his only rival in double digits is another political novice, Dr. Ben Carson.

Former frontrunner FL Gov. Jeb Bush has tumbled into eighth place despite his $100-million bankroll.

In a Gravis Marketing poll of 507 Iowa Republicans conducted last Friday and Saturday, Trump has 31.7 percent to Carson’s 15.8 and Bush’s 4.1 percent. A Monmouth University poll released yesterday had showed Trump and Carson running neck and neck with 23 percent – much to the excitement of the GOP establishment, including Fox News Channel.

But today’s Gravis poll seems more in line with other recent surveys in the Hawkeye State, where the first caucuses of 2016 will be held five months from today on Feb. 1.

Trump is dominant across almost all demographic groups, leading Carson and Cruz among Hispanics with 29 percent. He also won a plurality among GOP voters who described themselves as both pro-life and pro-choice, those in the 18-49 age group, and Republicans declaring themselves moderate or “slightly liberal.”

Among Roman Catholics in Iowa, the Presbyterian Trump polls 40 percent to 11 percent for Carson. Bush, a Catholic convert who often claims to be guided by his faith, polled at 0.8 percent among his coreligionists.

In Iowa, Trump trails only among evangelicals, with 13 percent to 26 percent for Carson and 22 percent for Cruz. Both Carson and Cruz are evangelicals themselves.

Doug Kaplan, managing partner of Gravis Marketing, the Florida-based company that conducted the survey, said that Carson continues to benefit from his steady, calm performance at the GOP debate in Cleveland Aug. 6.

“Our polling immediately after showed that Carson was the winner,” Kaplan said. “While the pundits missed it, it is really up to the voters to decide.”

Many of those same pundits, especially those on Fox, immediately declared Trump the loser of the debate, and at least one or two said it was the beginning of the end of his campaign. Instead, Fox’ favorites have plummeted in most surveys since the Trump-Fox dustup.

“Trump is pulling support from other candidates,” Kaplan said, “and is building a solid base of support.”

Iowa has open caucuses, which allow, say, Democrats or independents to declare themselves Republicans and vote on the GOP side. Of Trump’s declared supporters, 37 percent told Gravis they were Democrats, 37 percent independents, and only 26 percent Republicans.

On the Democrat side, despite Hillary Clinton’s continuing legal woes over her State Department emails, she maintains a strong lead in Iowa, with 45.1 percent to Vermont Sen. Bernie Sanders’ 16.9 percent and 13.4 percent for Vice President Joe Biden. Biden has promised a decision by the end of the month on whether he will seek the Presidency for a third time.

Former Gov. Martin O’Malley of Maryland got 4.9 percent of the Democrat vote, Sen. Elizabeth Warren, who huddled last week with Biden, had 4.6 percent. Former Sen. Jim Webb (1.2 percent) and former Gov. Lincoln Chafee of Rhode Island (0.5 percent) trailed.

Among Iowa Republicans, Trump now claims an 8-1 polling advantage over Bush, who this morning on Fox dismissed the New York real-estate mogul as “more Democrat than Republican.”

Yet another Republican insurgent, Texas Sen. Ted Cruz, who will appear at an anti-Iranian deal rally with Trump in Washington next week, is in third place with 6.9 percent.

The first Republican with any significant ties to the party’s consultant-industrial RINO complex to scratch was Sen. Marco Rubio. According to Gravis, he is in fifth place with 5.8 percent.

Gov. Scott Walker of Wisconsin, an Iowa native from a neighboring state who led the GOP field until recently, has now fallen to fifth place, with 5.6 percent, ahead of Gov. Bobby Jindal of Louisiana (5.2 percent) and Carly Fiorina (4.6 percent).

In eighth place, Bush is still ahead of former Arkansas Gov. Mike Huckabee, a former winner of the Republican caucuses in Iowa, with 2.6 percent.

Next come Gov. Chris Christie of New Jersey (2 percent), Gov. John Kasich of Ohio (1.4 percent), Sen. Rand Paul (1.3 percent), former Gov. Rick Perry of Texas (0.9 percent), former Sen. Rick Santorum (0.6 percent), Sen. Lindsey Graham of South Carolina (0.4 percent) and former Gov. George Pataki of New York (0.1 percent).

Of the 957 voters polled, 43 percent approved of President Barack Obama’s job performance, while 51 percent disapproved and 6 percent were unsure.