Ashley Kirk, Tom McCarthy and Helena Robertson report:
Even if Biden defeats Trump, he will be unable to pass legislation on key issues such as healthcare, immigration and climate change unless the Democrats simultaneously seize the Senate, where the Republicans now have a 47-53 majority.
The Democrats could pull it off. Democratic challengers in two states, Arizona and Colorado, appear to have a good chance in defeating Republican incumbents, while only one Democratic incumbent, in Alabama, looks especially vulnerable, according to the latest forecast from the Cook Political Report.
The number of additional seats the Democrats need to win for a voting majority depends on who wins the White House, since any Senate tie of 50-50 is broken by the sitting vice-president. If Trump wins re-election, the Democrats probably need three states, in addition to Arizona and Colorado, for the majority; if Biden wins, the Democrats probably need only two more.