The poll also shows President Obama leading Mitt Romney, 51 percent to 45 percent. The poll was conducted partly before Tuesday's debate and partly after. Wisconsin's Senate race is expected to be among the closest in the nation, and outside groups are pummeling both candidates over the airwaves. Thompson just told the Milwaukee Journal Sentinel he put $850,000 of his own money into the contest for the final stretch. The NBC News/Wall Street Journal/Marist poll was conducted Oct. 15-17, surveying 1,013 likely voters. The margin of error is plus-or-minus 3.1 percentage points.