Newt Gingrich’s surge in the polls isn’t limited to just the early presidential-nominating contest of Iowa.

According to new NBC News-Marist polls, the former House speaker has now opened up commanding leads in South Carolina and Florida -- two states that historically have played important roles in deciding the eventual Republican nominee.

Fueled by the support from conservatives and the Tea Party, Gingrich is ahead of former Massachusetts Gov. Mitt Romney by nearly 20 points in South Carolina.  The winner of that state's primary has gone on to capture each GOP nomination since 1980.

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And he leads Romney by double digits in Florida, whose primary ultimately ended up deciding the party’s pick in 2008.

“You can see why the Romney people are getting a little itchy,” said Lee Miringoff, the director of Marist College’s Institute for Public Opinion, referring to the Romney campaign’s recent attacks on Gingrich.

Gingrich ahead “any way you slice it”
In South Carolina, which holds its presidential contest on Jan. 21, Gingrich gets the support of 42 percent of likely primary voters, including those leaning toward a particular candidate. That’s a 35-point jump since October’s NBC-Marist poll of the Palmetto State contest.

Romney gets 23 percent (a five-point drop), and no other Republican candidate registers in double digits. Texas Rep. Ron Paul gets 9 percent, while Texas Gov. Rick Perry and Minnesota Rep. Michele Bachmann are tied at 7 percent.

In a field reduced to three candidates in South Carolina, Gingrich gets the support of 48 percent of likely voters, Romney gets 30 percent and Paul gets 12 percent.

In a simple two-way race, Gingrich’s support increases to 57 percent and Romney’s moves to 33 percent.

“It’s a good lead [for Gingrich] any way you slice it,” Miringoff says.

Read the full NBC-Marist South Carolina poll

In Florida, which holds its primary on Jan. 31, Gingrich is at 44 percent among likely voters -- a 38-point increase from October. He’s followed by Romney at 29 percent (a four-point decline), Paul at 8 percent and Perry at 4 percent.

In a three-way race in the Sunshine State, it’s Gingrich 51 percent, Romney 31 percent and Paul 10 percent. And in a simple head-to-head contest, it’s Gingrich 54 percent, Romney 36 percent.

Read the full NBC-Marist Florida poll

Tea Party power
According to the two polls, Gingrich performs especially well among the most conservative primary voters.

Among Tea Party supporters -- who make up about half of all likely primary voters in South Carolina and Florida -- the former House speaker leads Romney by more than 30 percentage points in both states (51-20 percent in South Carolina and 57-22 percent in Florida).

Gingrich also enjoys huge leads among “conservative” and “very conservative” voters.

By comparison, Romney bests Gingrich among liberals and moderates in Florida (39 percent to 29 percent), and essentially ties him among these GOP voters in South Carolina (with Gingrich’s 29 percent to Romney 26 percent).

And Gingrich has the most intense support. In South Carolina, 50 percent of his backers strongly support him, versus 34 percent who strongly support Romney,

In Florida, 60 percent of Gingrich’s backers strongly support him, compared with 38 percent for Romney.

If there’s a silver lining in these polls for Romney, it’s that more than half of Gingrich’s supporters in both states picked the former Massachusetts governor as their second-choice pick. And only a fraction of likely GOP primary voters in South Carolina and Florida view Romney as an unacceptable candidate.

This means Romney could potentially gain more support if his campaign is able to raise doubts about Gingrich, Miringoff says.

Obama’s standing improves in Florida
Turning to the general election, President Obama’s standing has improved in Florida, always a key presidential battleground state. 

Forty-six percent of registered voters in the state approve of his job, which is up five points since October.

In hypothetical match-ups, the president leads Romney by seven points (48 to 41 percent) and Gingrich by 12 points (51 to 39 percent).

In South Carolina -- a reliable Republican state in presidential contests -- Obama’s approval rating stands at 44 percent, and he holds narrow leads over Romney (45 to 42 percent) and Gingrich (46 to 42 percent). 

The South Carolina survey was conducted Dec. 4-6 of 2,107 total registered voters (with a margin of error of plus-minus 2.1 percentage points) and of 635 likely Republican primary voters (plus-minus 3.9 percentage points).

The Florida poll was conducted Dec. 4-7 of 2,119 total registered voters (with a margin of error of plus-minus 2.1 percentage points) and of 469 likely Republican primary voters (plus-minus 4.5 percentage points).