Six days before crucial Republican presidential primaries in Michigan and Arizona, new polls indicate it's all tied up in Michigan between Mitt Romney and Rick Santorum, with Romney leading Santorum in Arizona.

According to an NBC News-Marist survey released Wednesday morning, 37 percent of people likely to vote in Michigan's Republican presidential primary say they are backing former Massachusetts Gov. Romney, with 35 percent supporting former Sen. Santorum of Pennsylvania. Romney's two-point advantage is well within the poll's sampling error. The survey indicates that 13 percent are backing Rep. Ron Paul of Texas, with 8 percent supporting former House Speaker Newt Gingrich.

Polls released last week in Michigan indicated Santorum with a slight lead over Romney.

Santorum surged in state and national polling after sweeping the Feb. 7 contests in Colorado, Minnesota and Missouri.

Michigan, where Romney was born and his father served as governor of the state in the 1960s, is turning into a make-or-break state for him to win. The 30 delegates up for grabs in Michigan's Feb. 28 primary will be divided proportionally.

In Arizona, which holds its primary on the same day as Michigan, Romney appears to have a larger lead, according to the NBC News-Marist survey. Forty-three percent of people likely to vote in the state's GOP presidential contest say they are backing Romney, with 27 percent supporting Santorum, 16 percent backing Gingrich and 11 percent behind Paul.

A CNN/Time/ORC poll released Tuesday indicated a closer race in Arizona, with Romney at 36 percent, Santorum at 32 percent, Gingrich at 18 percent and Paul at 6 percent. Romney's four-point advantage is within the survey's sampling error.

The 29 delegates at stake in Arizona will be winner-take-all.

The NBC News-Marist survey's release comes just hours before the four candidates face off at a GOP presidential debate hosted by CNN and the Republican Party of Arizona at the Mesa Arts Center.

Looking ahead to the general election, the survey indicates President Barack Obama holding double digit leads over his GOP competitors in hypothetical November matchups, with Obama slightly trailing the leading Republicans in Arizona.

The NBC News-Marist poll in Michigan was conducted Feb. 19-20, with 3,149 registered voters, including 715 likely Republican primary voters, questioned by telephone. The survey's sampling error for GOP primary questions is plus or minus 3.7 percentage points, with an overall sampling error of plus or minus 1.8 percentage points.

The NBC News-Marist poll in Arizona was conducted Feb. 19-20, with 2,487 registered voters, including 767 likely Republican primary voters, questioned by telephone. The survey's sampling error for GOP primary questions is plus or minus 3.5 percentage points, with an overall sampling error of 2 percentage points.