Elections in New York show: The problem for the Democrats is Biden. As a result of his victory, the Republicans will lose a seat.
Suozzi's victory reveals a problem to Biden: the issue of migration. The refugees at the Mexican border are the biggest point of contention in the current political climate in the USA. Biden more unpopular than ever - the refugee crisis is the most important issue. And some Democrats are distancing themselves from the president. If "Biden's poll numbers don't improve" then Democrats in swing districts will focus more on local issues.