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Less than a year before the first presidential contests begin, a trio of new NBC News/Marist polls show that the Republican race is wide open in the early nominating states of Iowa, New Hampshire and South Carolina.

In fact, seven different possible Republican candidates get double-digit support in at least one of the states. But only two candidates — former Florida Gov. Jeb Bush and Wisconsin Gov. Scott Walker — are in double digits in all three states.

The early betting line for these critical states “points to a rough-and-tumble Republican nomination battle,” says pollster Lee Miringoff, director of the Marist College Institute for Public Opinion.

In Iowa, former Arkansas Gov. Mike Huckabee leads the GOP pack getting support from 17 percent of potential Republican caucus-goers, followed by Bush at 16 percent, Walker at 15 percent, New Jersey Gov. Chris Christie at 9 percent and Sen. Rand Paul, R-Ky., at 7 percent.

In New Hampshire, Bush gets support from 18 percent of potential GOP primary voters, followed by Walker at 15 percent, Paul at 14 percent and Christie at 13 percent.

And in South Carolina, it’s native son Sen. Lindsey Graham, R-S.C., at 17 percent, Bush at 15 percent, Walker at 12 percent, and Huckabee and retired neurosurgeon Ben Carson tied at 10 percent.

Clinton holds a substantial lead in the early states

By comparison, the Democratic nomination contest is much less competitive in these three states. In Iowa, former Secretary of State Hillary Clinton leads Vice President Joe Biden by more than 50 points, 68 percent to 12 percent.

She’s ahead of Sen. Bernie Sanders, I-Vt., by the same margin in New Hampshire, 69 percent to 13 percent.

And in South Carolina, Clinton has a 45-point advantage over Biden, 65 percent to 20 percent.

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The NBC/Marist polls did not include Sen. Elizabeth Warren, D-Mass., in these trial heats because she continues to insist — in both the present and future tenses — that she won’t be running for president in 2016.

All of the possible candidates that the polls measured either have formed committees to explore a run, have begun to hire staff, or at least have left open the possibility of a White House bid.

An early look at the general election

In hypothetical general-election matchups among registered voters, Clinton leads both Bush and Walker in the battlegrounds of Iowa and New Hampshire.

In Iowa, Clinton holds an eight-point advantage over Bush, 48 percent to 40 percent, and an 11-point edge over Walker, 49 percent to 38 percent.

In New Hampshire, Clinton is up by six points over Bush (48 percent to 42 percent) and seven points over Walker (49 percent to 42 percent).

And in the GOP-leaning state of South Carolina, Bush leads Clinton by three points, 48 percent to 45 percent. And Walker ties her at 46 percent each.

While Clinton is ahead in Iowa and New Hampshire, President Barack Obama isn’t much of an asset for her in these two states, with his job-approval rating at 43 percent in both.

Obama’s job rating is one point higher in South Carolina, at 44 percent.

Testing the most acceptable and least acceptable issues

The NBC/Marist polls also tested seven key issues — supporting Common Core, supporting a pathway to citizenship for undocumented immigrants, wanting to repeal the federal health-care law, believing that climate change is man-made, opposing gay marriage, favoring raising taxes on the wealthy and wanting to send more U.S. troops to combat ISIS — to see which were the most acceptable and unacceptable to voters in these three states.

The most acceptable among all registered voters and Democrats: a candidate who wants to raise taxes on the wealthy.

The least acceptable among all registered voters and Democrats: a candidate who opposes same-sex marriage.

The most acceptable among Republican voters: a candidate who wants to repeal the health-care law.

The least acceptable among Republicans: believing climate change is man-made (in Iowa and South Carolina) and raising taxes on the wealthy (New Hampshire).

The NBC/Marist of Iowa was conducted Feb. 3-10 of 891 registered voters (margin of error of plus-minus 3.3 percentage points), 320 potential GOP caucus-goers (plus-minus 5.5 percentage points) and 321 potential Democratic caucus-goers (plus-minus 5.5 percentage points).

The NBC/Marist poll of New Hampshire was conducted Feb. 3-10 of 887 registered voters (margin of error of plus-minus 3.3 percentage points), 381 potential GOP primary voters (plus-minus 5.0 percentage points) and 309 potential Democratic primary voters (plus-minus 5.6 percentage points).

The NBC/Marist poll of South Carolina was conducted Feb. 3-10 of 877 registered voters (plus-minus 3.3 percentage points), 450 potential GOP primary voters (plus-minus4 4.6 percentage points) and 352 potential Democratic primary voters (plus-minus 5.2 percentage points).