I have not looked at other states but if Hennepin is Minnesota's bellwether county the term has no meaning. I don't care how long a "winning" streak they have, if a county votes 40 points one way or the other from the state results it is not a bellwether. The definition of a bellwether county as I have always understood it is a county that usually matches the statewide margin. It's not perfect but Nicollet County probably is the best fit to that definition in Minnesota.
They both matter.
A bellwether is, first and foremost, one which carries for a winner [winning party] over a long period of time.
The margins being in proximity with the result…that bolsters an argument for citing a bellwether as such.
Sometimes, the margin can be not in proximity in a given election cycle. For example: In 1988, Nevada carried for Republican winner George Bush by +21.06 when he won nationwide by +7.72 percentage points. Nowhere near to looking like a bellwether, as your comment describes, but the state carried for the winner. And when Bill Clinton won a Democratic pickup of the presidency in 1992, and unseated Bush, among his Democratic pickups was Nevada. The state has voted the same as New Mexico, with exception of 2000 (separate winners for U.S. President and U.S. Popular Vote), since that state joined the union and first voted in 1912. They carried for all winners through 1972 and resumed in the 1980s and 1990s. They realigned to the Democrats with Barack Obama’s Democratic pickup of the presidency in 2008.
Minnesota joined the union and first voted in 1860. The elections in which Hennepin County did not carry for the statewide winner, for U.S. President, were in 1916 and 1960. According to
Wikipedia, it states that in 1912 the former Republican U.S. president and Progressive Party nominee Teddy Roosevelt, who carried Minnesota, won Hennepin County. That is, according to the below image’s list; but, the website’s map says it carried for Woodrow Wilson.
I would argue that Hennepin County can carry for a Democrat while the state of Minnesota ends up in the Republican winner’s column for U.S. President—which I anticipate is coming (given the state votes the same as New Hampshire and they are in proximity to the
Rust Belt Bellwether Trio)—because the county’s margins are nowadays way outside statewide results. Hennepin County, in 2020, voted like my home state Michigan’s Wayne County.