Okay, I might have oversold it. It probably won’t matter. Over the last few administrations there have been a handful of non-budgetary pieces of legislation passed. Dodd-Frank, the ACA, Trump’s 2017 tax cut, and the First Step Act. Not a single one of these was passed by a divided Congress. The only exception to this rule is COVID-19 pandemic relief but that provides a fairly obvious exception to the rule: split Congresses are too partisan to pass legislation.
Even united Congresses struggle to pass important legislation. The ACA took months of negotiations between democrats to pass. A republican Congress failed to pass healthcare reform and passed the 2017 tax cuts by the skin of its teeth.
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Unless either President Donald Trump or President Joe Biden manage to get a united Congress to start their administration their legislative agenda will almost certainly die before they are even sworn in. No President in the modern era has gotten their party to control Congress if they didn’t control it off the bat. I.e. if you come in without Congress on your side then it never will be.
At this point, my argument takes a little prognosticating. I think democrats will maintain the House of Representatives and republicans will hold the Senate in 2020. I’ll even go out on a limb and say in 2022, the party which doesn’t control the White House will take control of Congress.