Remember that big GOTV infrastructure left over from Scott Walker’s resounding victory in the recall election, just three months ago?  The infrastructure that was supposed to grease the skids for a Republican victory in Wisconsin for both Mitt Romney and Tommy Thompson, the latter in the Senate race that replaces retiring Democrat Herb Kohl?  Today’s Rasmussen poll suggests that it might be more difficult for Republicans to win the Badger State than previously thought:

Democratic Congresswoman Tammy Baldwin now has a slight lead over former Republican Governor Tommy Thompson in Wisconsin’s volatile U.S. Senate race.

A new Rasmussen Reports telephone survey of Likely Wisconsin Voters finds Baldwin with 49% support to Thompson’s 46%. Two percent (2%) like some other candidate in the race, and four percent (4%) are undecided.

The Wisconsin race now shifts from Safe Republican to a Toss-Up in the Rasmussen Reports Senate Balance of Power rankings.

Thompson enjoyed a bounce after winning his primary last month. Now the race has returned to where it was in July when Baldwin posted leads over all her potential Republican opponents including Thompson. This marks Baldwin’s highest level of support to date.

President Obama also has regained the lead in Wisconsin after Mitt Romney had edged ahead in the state last month. Wisconsin remains a Toss-Up in the Rasmussen Reports Electoral College Projections.

How is Baldwin managing to pull out in front?  She has a seven-point lead among independents, 46/39, and a +5 in the overall gender gap.  In the age demos, most of her lead comes from a ten-point gap in the under-40 vote, 50/40, while Thompson only leads among seniors by six, 51/45.

Of course, this is still a margin-of-error race, and the two candidates are evenly matched in favorability as well.  Thomspon gets a 49/46 personal rating, while Baldwin has a slightly wider 49/44 favorability.  Baldwin’s numbers show a greater polarization, though, with 32/31 on very favorable/very unfavorable, while Thompson has a 22/28 rating — indicating his support is significantly less passionate, while his opposition is somewhat more so.

In even more bad news, the polling sample slightly overstates Republican turnout.  The recall election had a D/R/I in the exit polls of 34/35/31, with Walker’s big GOTV apparatus in place.  Rasmussen’s sample is 36/39/25, which is slightly more Republican and less independent.  That seems rather optimistic in a regularly-scheduled general election; the 2010 midterm exit polls in Wisconsin had a D/R/I of 37/36/28.  The difference is small, and it’s not indefensible — we may see a big surge in Republican voters — but it still should favor Thompson, and he’s still trailing.