Until the “outspent” paradigm changes the Democrats will keep chasing the GOP further rightward. Sanders is the first non third party candidate to threaten the “outspent” paradigm.
Gerrymandering was a secondary driver that firmly placed the GOP in control of Congress until 2022. The primary driver was Obama following the Democratic Leadership Council (DLC) playbook that Bill Clinton followed by shoving through a GOP initiated program during his first term. In Bill Clinton’s case it was NAFTA, in Obama’s case it was his Affordable Care Act (ACA). GOP candidates don’t win because a lot more Murkins vote for them, they win when a lot more left leaning voters stay home and don’t vote.
From its inception in 1985 the DLC understood that sustained corporate cash flow was impossible with a long standing Democratic Party controlled Congress. Bill Clinton and Obama kept GOP controlled Congress in place as much as possible to give them cover to deliver for the 1% at the expense of the 99%.