Former Wisconsin Sen. Ross Feingold leads incumbent Republican Sen. Ron Johnson 47 percent to 41 percent among likely voters in the Badger State, according to the latest Marquette Law School poll.

Feingold, a Democrat, held this seat for three terms before losing to Johnson in 2010. 

In late August, the same survey gave Feingold a more modest 3-point edge, 48 percent to 45 percent. The current RealClearPolitics average of polls from Aug. 27 to Sept. 20 has Feingold ahead by 9.7 points. 

Eight percent of voters in the Marquette poll said they didn’t have a preference.

[Rating Change: Wisconsin Senate Race Moves to Democratic Column]

The survey also found that when the Libertarian candidate Phil Anderson is included, Feingold maintains a 5-point lead over Johnson, 44 percent to 39 percent, with Anderson receiving 7 percent among likely voters.

The poll surveyed 677 likely voters and 802 registered voters by landline or cell phone from Sept. 15 through Sept. 18. The margin of error for the likely voter sample was 4.8 percentage points.

The Rothenberg & Gonzales Political Report/Roll Call rates the race as Tilts Democratic.