Washington (CNN) Donald Trump's support continues to grow among those who say they are likely to participate in February's Iowa presidential caucuses and Ted Cruz is on the rise while Ben Carson loses ground in the state, a new CNN/ORC Poll finds .

Overall, Trump has 33% support among likely GOP caucusgoers, followed by Cruz at 20% with Carson at 16%, Florida Sen. Marco Rubio at 11% and former Florida Gov. Jeb Bush at 4%. The new poll shows Trump up 8 points, Cruz up 9, while Carson has faded by 7 points, compared with the last CNN/ORC poll, conducted in late October and early November

The poll finds a markedly different landscape among potential GOP caucusgoers than another Iowa poll released Monday by Monmouth University . The difference between the two seems to stem primarily from sampling.

The Monmouth poll interviewed a sample drawn from registered voter lists that primarily comprised those who had voted in state-level Republican primary elections in previous election years. Among those voters, Monmouth found Cruz and Rubio ahead of Trump and Carson. Among voters who were not regular GOP primary voters, however, the poll found Trump ahead, similar to the CNN/ORC poll's finding.

The CNN/ORC Poll drew its sample from Iowa adults, asking those reached about their intention to participate in their caucus, interest in news about the caucuses, and past participation patterns to determine who would be a likely voter.

But still, Trump's lead holds even among only those voters who express the most interest in attending the caucus or the most regular past participation in presidential caucuses. Among those in the CNN/ORC poll who say they definitely plan to attend the caucuses and are more interested in news about them than any other news story -- a group which represents approximately 8% of Iowa adults -- Trump's lead grows to a 42% to 23% advantage over Cruz, with Rubio at 11% and Carson at 9%.

And among those who say they have participated in almost all of the caucuses for which they have been eligible -- about 10% of Iowa adults -- Trump leads 38% to 21% for Cruz, with Carson at 12% and Rubio at 11%.

One group that remains a challenge for Trump and which makes up a large share of Iowa's usual set of Republican caucusgoers is white evangelicals. Among that group, 26% back Cruz, 24% Trump, 20% Carson and 12% Rubio. In last month's poll, Trump trailed Carson 31% to 20% among white evangelicals, with Cruz at 15% and Rubio at 11%.

Trump is increasingly seen by likely GOP caucusgoers as the Republican with the best chance to win the 2016 general election: 42% say Trump has the best shot, followed by 17% for Cruz and 11% each for Carson and Rubio. Last month, 33% thought Trump had the best chance to win followed by Carson at 25% and Rubio at 17%. Cruz is up 9 points on this question.

As is the case nationally, Trump holds big advantages as the candidate more trusted to handle the economy and illegal immigration, with smaller though still substantial leads on handling ISIS and foreign policy (30% Trump to 21% Cruz, 13% Rubio and 9% Bush). On foreign policy, Trump has increased his advantage on that issue since the early-November poll, when 18% said they thought Trump would do the best job and 14% each Cruz, Rubio and Bush, with Carson at 11%.

But Trump's advantage on foreign policy and handling ISIS is larger than his edge on handling the responsibilities of being commander-in-chief. There, Trump comes in at 28% with Cruz a close second with 22%, Carson follows at 13% with Bush at 10% and Rubio at 9%.

Trump remains somewhat vulnerable on social issues, where Carson (21%) is most trusted, but here, too, Trump has increased his support. In November's poll, 13% said Trump would do the best job on social issues, that's risen to 19%. Cruz follows Carson and Trump on this question with 17%. Trump and Cruz are also nearly even when caucusgoers are asked who best represents the values of Republicans like yourself (25% Trump to 22% Cruz, Carson fades 7 points to 18%).

On the Democratic side, Hillary Clinton maintains an 18-point lead over Vermont Sen. Bernie Sanders, 54% to 36%. Former Maryland Gov. Martin O'Malley has 4%.

The gender gap between Clinton and Sanders has narrowed in the last month, with both men and women breaking significantly in the former secretary of state's favor (51% Clinton to 40% Sanders among men, 57% Clinton to 34% Sanders among women; last month it was 48% Clinton to 44% Sanders among men and 62% Clinton to 31% Sanders among women).

Clinton's edge on handling economic issues is smaller in Iowa than it is nationally, 47% in Iowa say they think Clinton would do the best job handling the economy while 42% say they trust Sanders most, while our recent national poll found Clinton holding a 58% to 31% advantage on the same issue. Likewise, Iowa's likely caucusgoers are more likely to think that Sanders would do the most to help the middle class (50%) than to say Clinton would (43%), a question that split national Democrats almost evenly (47% Clinton to 44% Sanders).

Likely Democratic caucus-goers remain more focused on the economy than on terrorism or foreign policy. The poll finds 38% say the economy will be most important when deciding their vote for president, compared with 13% who cite terrorism and 10% who name foreign policy their top issue. Among Republican caucus-goers, about as many say terrorism is their top issue (27%) as cite the economy (29%).

The Iowa poll finds Clinton remains dominant on health care, race relations, foreign policy issues and as having the best chance to win. She also holds a better than 3-to-1 lead as the candidate who would best handle ISIS. But the two are about evenly matched on which better represents the values of "Democrats like yourself," with 46% naming Clinton, 44% Sanders.

The CNN/ORC Poll was conducted by telephone November 28-December 6 among 2,003 adult residents of Iowa, including interviews with 552 likely Republican presidential caucusgoers and 442 likely Democratic presidential caucusgoers. Results for likely Democratic caucusgoers have a margin of sampling error of plus or minus 4.5 points, it is 4 points for likely Republican caucusgoers.