Some may ask why Democrats do not return to positions that appeal to rural voters.
Recall how Mr Obama won the presidency opposing gay marriage
and Bill Clinton built a coalition in the centre-ground.
But rancorous political disputes—over guns, abortion and climate change—
split so neatly along urban-rural lines that parties and voters increasingly sort themselves into urban-rural tribes.
Gerrymandering and party primaries reward extremists, and ensure that, once elected, they seldom need fear for their jobs.
The incentives to take extreme positions are very powerful.
Bitter partisanship, ineffective federal government and electoral bias poison politics and are hard to fix.
Changing the constitution is hard—and rightly so.
Yet the voting system for Congress is easier to reform than most people realise,
because the constitution does not stipulate what it should be. Congress last voted to change the rules in 1967.
The aim should be to give office-seekers a reason to build bridges with opponents rather than torch them.
If partisanship declined as a result, so would pressure on voters to stick to their tribe.
That could make both parties competitive in rural and urban areas again, helping to restore majority rule.
One option, adopted in Maine this year and already proposed in a bill in Congress for use nationwide,
is "ranked-choice voting" (RCV), in which voters list candidates in order of preference.
After a first count, the candidate with the least support is eliminated,
and his or her ballots are reallocated to those voters'second choice.
This continues until someone has a majority.
Candidates need second- and third-choice votes from their rivals'supporters,
so they look for common ground with their opponents.
Another option is multi-member districts, which were once commonplace and still exist in the Senate.
Because they aggregate groups of voters, they make gerrymandering ineffective.
Voting reform is not the whole answer to partisanship and built-in bias, but it would help.
It is hard, but not outlandish.
To maintain the trust of all Americans, the world's oldest constitutional democracy needs to reform itself.