Heller leads Berkley 48 percent to 43 percent in Washoe County, the state's battleground county. Berkley, whose district is Las Vegas-based, needs to keep the margins close there. She has spent significant time campaigning up north (and money advertising there), introducing herself to voters. And the two candidates are tied in Berkley's home county of Clark, with both taking 47 percent. Berkley is winning 53 percent of non-white voters to Heller's 37 percent. The poll has President Obama leading Mitt Romney by a narrow margin, 49 percent to 47 percent. But Obama is performing much better than Berkley among non-white voters, taking 67 percent to Romney's 30 percent in heavily Latino Nevada. Pollsters did not interview respondents in Spanish, Hotline On Call was told. Berkley is also lagging behind Obama in Washoe: He is winning the county, taking 55 percent to Romney's 43 percent. And while Heller is matching Berkley in Clark, Obama is beating Romney 52 percent to 45 percent there. The House Ethics Committee's July decision to investigate Berkley over whether she used her position in Congress to help her husband financially was expected to make the race an uphill climb for Berkley -- and both Heller and Crossroads GPS have pummeled her over the airwaves on it -- but the polls didn't show movement over the summer. The NBC News/Wall Street Journal/Marist poll was conducted Sept. 23-25 and surveyed 984 likely voters, for a margin of error of plus-or-minus 3.1 percentage points.