UPDATED Wednesday, September 19, 2012 --- 12:44 p.m.
POSTED: Wednesday, September 19, 2012 --- 8:40 a.m.

MADISON, Wis. (AP) -- Outside groups are spending big as the race for an open Wisconsin Senate seat shows signs of tightening.

Independent groups have poured nearly $8.8 million into the race so far, based on a tally by the nonpartisan Center for Responsive Politics.

Two new polls released Wednesday show that Democrat Tammy Baldwin appears to have closed the gap and perhaps taken the lead from Republican former Gov. Tommy Thompson.

A poll by Quinnipiac University shows both Baldwin and Thompson with 47 percent support. Thompson had led 50 percent to 44 percent in the last poll done a month ago.

But a Marquette University Law School poll has Baldwin leading 50 percent to 41 percent. That poll had a 4.2 percentage point margin of error.

Copyright 2012: Associated Press