The polls were conducted July 14-21 – so before and after Trump's controversial comments belittling John McCain's war record on July 18. And they suggest the comments didn't affect Trump in Iowa (he was at 16 percent before the comments and 18 percent after), but they did hurt him in New Hampshire (26 percent before, 14 percent after).
Despite his poll position, Trump's favorable/unfavorable rating among Iowa Republicans is just 45 percent/44 percent, and it's 39 percent/53 percent among GOP voters in New Hampshire.
Hillary leads big in Iowa – but by a smaller margin in New Hampshire
Meanwhile, in the Democratic presidential race, the polls show that Hillary Clinton is ahead, but that Bernie Sanders has gained ground on her since earlier this year.
In Iowa, Clinton leads Sanders by 29 points, 55 percent to 26 percent, with Martin O'Malley at 4 percent and Jim Webb at 2 percent. In a February NBC-Marist poll of the Hawkeye State, Sanders was just 7 percent in a field that also included Vice President Joe Biden, who isn't expected to run for president.
In New Hampshire, Clinton is ahead of Sanders (who represents neighboring Vermont in the U.S. Senate) by 13 points, 47 percent to 34 percent. They're followed by O'Malley at 5 percent and Lincoln Chafee at 2 percent.
Back in February, Sanders was at 13 percent.
Both Clinton and Sanders are popular among Democrats in these two states. Clinton's fav/unfav is 74 percent/20 percent in Iowa (+54), and it's 71 percent/23 percent in New Hampshire (+48).
Sanders' is 54 percent/15 percent in the Hawkeye State (+39), and 65 percent/14 percent in the Granite State (+51).
But among all registered voters in these two presidential battleground states, the NBC-Marist polls finds that almost all of the major presidential candidates are unpopular – and that's especially true for Clinton.
The favorable/unfavorable scores in Iowa among all registered voters:
Sanders +3 (30 percent/27 percent)
Rubio -1 (31 percent/32 percent)
Walker -1 (30 percent/31 percent)
Bush -12 (34 percent/46 percent)
Clinton -19 (37/56 percent)
Trump -28 (32 percent/60 percent)
Notably, Clinton's fav/unfav score in Iowa among all registered voters mirrors what a recent Quinnipiac poll of the state found .
The favorable/unfavorable scores in New Hampshire:
Sanders +12 (41 percent/29 percent)
Bush -5 (40 percent/45 percent)
Walker -6 (28 percent/34 percent)
Rubio -6 (28 percent/34 percent)
Clinton -20 (37 percent/57 percent)
Trump -40 (27 percent/67 percent)
The NBC-Marist polls also find that President Barack Obama is unpopular in both states. His approval rating stands at 43 percent in Iowa and 41 percent in New Hampshire.
And his fav/unfav numbers are upside down in both states – 46 percent/51 percent in Iowa (-5) and 43 percent/53 percent in New Hampshire (-10).
Finally, the polls show that majorities of voters in the two states (61 percent in Iowa, 55 percent in New Hampshire) agree with the statement – originally made by former First Lady Barbara Bush – that the country has had enough Bushes and Clintons in the White House, and it's time to give someone else a chance.
The NBC-Marist poll of Iowa was conducted July 14-21 of 919 registered voters (+/- 3.2 percentage points), 342 potential GOP caucus-goers (+/- 5.3 percentage points) and 320 potential Democratic caucus-goers (+/- 5.5 percentage points).
The NBC-Marist poll of New Hampshire was conducted July 14-21 of 910 registered voters (+/- 3.2 percentage points), 401 potential GOP primary voters (+/- 4.9 percentage points) and 329 potential Democratic primary voters (+/- 5.4 percentage points).
View the full Iowa poll here.
View the full New Hampshire poll here.