Wisconsin Democratic Senate candidate Russ Feingold has a slight edge over Republican incumbent Sen. Ron Johnson, a new Marquette University poll shows.

Feingold held a 4-point lead in the poll, 46 percent to 42 percent, but the advantage is within the poll’s 4.5 percent margin of error.

Of the 803 registered voters polled from Aug. 25 to 28, 33 percent said they had a favorable opinion of Johnson while 34 percent said their opinion of him was unfavorable. Feingold had slightly better numbers — 40 percent favorable to 35 percent unfavorable.

But 30 percent said they haven’t heard enough about the incumbent to decide, while 23 percent said the same about Feingold.

Feingold’s lead in the Marquette poll has shrunk over the last two months. He led by 7 points in July and by 6 in early August.