Sabato’s Crystal Ball Report from the University of Virginia’s Center for Politics points out how difficult it will be for Wisconsin Republicans to unseat Democratic Senator Tammy Baldwin. The respected political forecast report named after Professor Larry Sabato puts the senate race in Wisconsin as “leans Democrat,” partly because of the strong midterm election effect.

In the 26 midterm elections from 1914 to 2014, Crystal Ball reports, “91% (287 of 314) of non-presidential party incumbents won reelection in midterms.”

“If anything, out-party incumbents losing in a midterm is becoming less common: In six of the last eight midterms, including the last three (2006, 2010, and 2014), no such incumbent lost reelection,” Crystal Ball said. “The last three midterms were all conducted under presidents with weak popularity (George W. Bush in 2006, and Barack Obama in 2010 and 2014).”

The Crystal Ball Report looked at the Wisconsin race more closely to see if it could be a possible pick up for the Republicans despite President Donald Trump’s relative unpopularity:

A potentially better Republican target is Wisconsin, given that Sen. Tammy Baldwin (D) is only running for her second term and the GOP state organization there is quite strong. The candidate field is not that clear, though, and there could be a bitter primary among state Sen. Leah Vukmir, Marine veteran Kevin Nicholson (an ex-Democrat backed by the economically conservative Club for Growth), and others. Baldwin benefited from a tough, late GOP primary in 2012, and the 2018 primary will also be in August.

The Badger State, along with Michigan and Pennsylvania, were the difference in last year’s presidential election: had Clinton won all three states, which were decided by a combined 77,744 votes, she would have been president. Trump’s approval ratings in all three states are in the low 40s or worse, so he could be a drag there, just like Barack Obama was in 2010 when, just two years after all three states gave him comfortable victories, they swung heavily to the Republicans at the gubernatorial and federal levels (and then again voted for Obama in 2012). In politics, things can change in a hurry.

In 2016, US Senator Ron Johnson actually out-performed Trump. Trump won with 47.9 percent of the vote to Hillary Clinton’s 46.9 percent. Johnson won with 50.2 percent of the vote over Russ Feingold’s 46.8 percent. Johnson received nearly 70,000 more votes than Trump.

The Crystal Ball Report does note that the election map nationally favors the Republicans because of the number of incumbent Democrats up for re-election:

Applying the historical averages to next year’s Senate elections would result — drumroll please — in a net party change of…zero seats. If 91% of the Democrats/Democratic-caucusing independents are reelected, that would be 23 out of 25, and if 75% of the Republicans are reelected, that would be six of eight, leading to no net change.

Without making any predictions, such a scenario is plausible: Democrats could lose two of the incumbents defending dark red states, in states such as Indiana, Missouri, Montana, North Dakota, and West Virginia, but otherwise hold everything else, while Republicans could lose the only two seemingly vulnerable seats among their much smaller stable of incumbent-held states: Arizona and Nevada.