Hoekstra was the target of criticism earlier this month when he aired a television ad on some state television stations that many deemed racially insensitive. But because the main subject of the poll was the presidential primary, there were no questions about the TV ad included. The poll does show President Obama's approval rating in the state at 51 percent, and the president would lead former Massachusetts Gov. Mitt Romney by 18 percentage points among all registered voters. In Arizona, Flake leads, but a large percentage of voters remain undecided. Carmona actually edges Flake among independent voters, 31 percent to 29 percent, but a 40-percent plurality are undecided. Unlike in Michigan, the Democrat is unlikely to get a boost from the top of the ticket in Arizona, where Obama's approval rating is just 38 percent, and he trails Romney, 45 percent to 40 percent. The NBC News/Marist polls were conducted Feb. 19-20. In Michigan, the poll surveyed 3,149 registered voters with a margin of error of plus-or-minus 1.8 percentage points. In Arizona, 2,487 registered voters were surveyed, for a margin of error of plus-or-minus 2.0 percentage points.