> The percentage of the American population which is either Democrat or Republican is consistently[1] well[2] above[3] 90%[4]

Even if you read “voting for a D or R candidate in a Presidential general election” as “being a D or R”, and “eligible voters” as “the American population”, both which are clearly and wildly wrong, your evidence still doesn’t support your claim, because it has 98.2% of 66.2% = 65% of eligible voters, which is not “well above 90%”.

I'm not sure why you expect news to target people who aren't even in their coverage's audience.

Those links show that out of all Americans who vote in presidential elections, well above 90% vote for either a Democrat or a Republican. However, that does not mean that well above 90% of Americans are either Democrats or Republicans.

People lie. I'm not sure why you expect the media to sell to people's lies instead of selling to people's actions.

PS Americans also overwhelmingly vote either Democrat or Republican in non-presidential elections, even down to the city council level.

> PS Americans also overwhelmingly vote either Democrat or Republican in non-presidential elections

Americans overwhelmingly abstain rather than voting for any of the offered candidates, Democrat, Republican, or independent or minor party, in non-Presidential elections. 2018 had the highest midterm turnout since the before the Reagan era, and it reached the whole way up to 49%.

What do you mean by "people's actions"? If you mean voting, well, Democrats and Republicans get about the same number of votes in presidential elections, which does not seem to justify your view that "left" media bias just reflects the political leaning of the average American.

Except Democrats have been consistently beating Republicans in presidential elections. Click the links. Go back further if you want to. The Republican candidate has won the popular vote exactly once (in 2004) since 1990.

The Presidential election popular vote margin has not gone over 10 million votes in over three decades now, in a country that has averaged about 300 million residents over that time span. These are not margins that support the idea that the population as a whole skews left as much as mainstream media skews left.

Stated vs. Revealed preferences.