The rating change comes less than one month before Election Day, making it the closest Senate race of the five battleground states polled by the nonpartisan election forecaster. The most recent polling from the Cook Political Report shows Sen. Tammy Baldwin (D-WI) leading by just 2 percentage points over GOP challenger Eric Hovde, down from her 7-point lead in August. 

Other polling shows Baldwin with a healthier lead, such as a recent survey from the New York Times and Siena College showing the Democratic incumbent with a 7-point lead in late September. A Marquette Law School poll conducted around the same time also showed Baldwin with a 7-point advantage. 

Hovde’s rise in the polls comes as he has consolidated support among Republicans after emerging from a crowded primary field of Republican candidates, largely thanks to a coveted endorsement from former President Donald Trump. Since then, Hovde has also managed to win the support of some independent voters, which will be key in the battleground state. 

Baldwin still leads among independent voters — she holds 50% support from the voter bloc compared to Hovde’s 42% — but Hovde has made significant progress in recent months, swinging the group in his direction by 11 points since August, according to Cook Political Report polling. 

Wisconsin’s battleground status has prompted national Democrats to focus their attention there, including President Joe Biden, who will appear for an event in the Badger State on Tuesday. Baldwin, however, will not be present.

Meanwhile, the Senate race has become one of the most expensive in the country as both parties pour millions into the seat ahead of Election Day. Hovde was largely recruited because of his ability to self-fund his campaign, with the GOP challenger spending around $20 million since the start of his campaign. 

With Wisconsin’s latest rating change, it joins Ohio and Michigan in the toss-up category — all seats held by Democrats, giving Republicans an advantage to flip some crucial seats. Two other seats currently held by Democrats in Montana and West Virginia have shifted to lean Republican and solid Republican, respectively.

There are 34 Senate seats up for grabs in the 2024 election cycle. Of these, Democrats must defend 23, compared to just 11 for Republicans — and nearly all competitive seats are held by Democrats, putting them on the defensive as they try to maintain their slim majority.

Democrats hold a 51-49 majority in the Senate, with the advantage of having Vice President Kamala Harris as a tiebreaker vote if needed. As a result, Republicans only need to flip one Senate seat to win the majority should they win back the White House in 2024. If they don’t regain the Oval Office, the party needs to secure two extra Senate seats.