Why not just post the Politico article?
See other opinions about it.
Because that's not what the Politico article says.
Biden’s team fears the aftermath of a failed Ukrainian counteroffensive
Basically a rehash of all the other articles saying Ukraine's counter offensive might not produce a decisive result, and that if it does not, the USA might push Ukraine to seek a negotiated end to the war.
If Ukraine's offensive fails as badly as Russia's winter offensive, they are in trouble. They don't necessarily need to sever the land bridge to Crimea, but they certainly need to make significant gains, as in thousands of sq kilometers that include some strategically significant objectives.