WASHINGTON (CNN) -- The Republican presidential nomination is up for grabs at this point in the race, according to a trio of early-primary state polls that shows no potential candidate holding a clear lead.

The NBC News/Marist surveys, released Sunday, give former Florida Gov. Jeb Bush a slim lead in New Hampshire, former Arkansas Gov. Mike Huckabee a lead in Iowa and South Carolina Sen. Lindsey Graham a slight advantage in his home state.

Their leads, however, are all within the margin of error, indicating a tight race in the three key early nominating states.

In New Hampshire, Bush leads the pack with 18 percent support among potential Republican primary voters. Wisconsin Gov. Scott Walker takes 15%, Kentucky Sen. Rand Paul takes 14% and New Jersey Gov. Chris Christie draws 13% support.

Huckabee takes 17% support from potential GOP caucus-goers in Iowa, barely edging Bush, who nabs 16% support. Walker again draws the support of 15% of respondents, while Christie takes 9% and Paul draws 7%.

In South Carolina, Graham draws 17% support, while Bush takes 15% and Walker takes 12% support. Huckabee and neurosurgeon Ben Carson tie with 10% of respondents.

The surveys, though early in the nominating contest, may be most troubling for Bush. They suggest despite being well-known as the son and brother of two former presidents, and though he's emerged as the preferred candidate of the GOP establishment, Bush hasn't yet convinced the party's primary voters to get on board.

The South Carolina results, too, suggest even Graham's constituents are lukewarm about his presidential aspirations.

On the Democratic side, the contest looks far more settled --- former Secretary of State Hillary Clinton leads the field by 45% or more in all three states. NBC and Marist did not poll the preferred candidate of progressives, Massachusetts Sen. Elizabeth Warren, because she's repeatedly said she won't run.

The New Hampshire survey was conducted from Feb. 3-10 among 381 potential GOP primary voters and has a margin of error of 5%; the Iowa survey was conducted over the same period, among 320 potential GOP caucus-goers, and has a margin of error of 5.5%; and the South Carolina poll was conducted over the same period among 450 potential GOP primary voters and has a margin of error of 4.6%.