Conventional wisdom says the middle is disappearing from American politics. The Republicans have moved far to the right, the Democrats far to the left, and woe to moderate voters looking for politicians to represent their views.

The conventional wisdom is wrong. Democrats have not become radical leftists, or anything close to it.

You keep hearing this story partly because Republicans have an interest in promoting it and large parts of the news media find it irresistible. It’s a “both sides do it” angle that allows journalists to appear above partisan scrum. We love that image. The facts don’t support this case.

Look at this year’s primaries. Across the country, two Democratic incumbents in the House lost a primary. Zero Senate candidates did. In conservative states with moderate Democratic senators, not one moderate faced a serious primary challenge.

The situation was very different in 2010 with the Tea Party, which pushed the Republican Party to the right. Multiple incumbents lost that year. This year’s real story is the one the political scholars Lara Putnam and Theda Skocpol tried to tell: Anti-Trump activists have taken a strategic approach, backing moderate or progressive candidates, depending on the district.

It’s true a few proudly left-leaning Democrats won gubernatorial primaries, like Stacey Abrams in Georgia and Andrew Gillum in Florida. I encourage you to watch their speeches. They are strong candidates, and hardly socialists. The list of progressive insurgents who got thumped is longer.

In Congress, the party’s reaction to President Donald Trump tells a similar story. Pundits talk about “Trump derangement syndrome” — a condition, supposedly, in which his presidency has made Democrats go crazy. Except it hasn’t.

One example: There is strong evidence Trump broke the law, by obstructing justice and by using the presidency to enrich himself. Still, Democratic leaders refuse to push for impeachment. They say the country should wait for Robert Mueller’s investigation to finish. I think that’s wise and certainly not deranged.

Finally, there is policy. Democrats have moved to the left over the past few decades on social and economic issues. Democrats are focusing less on Bill Clinton’s themes of personal and fiscal responsibility, and more on using the government to help people.

Think about what a left-wing agenda would look like: top tax rates of 70 percent or higher. A universal basic income. The elimination of employer-provided health insurance. These ideas remain on the margins.

The radical agenda is the Republican agenda: make climate change worse. Aggravate inequality. Sabotage health-insurance markets. Run up the deficit. Steal a Supreme Court seat. Keep minorities from voting.

If you consider yourself a moderate, your choice in this year’s midterms is clear. If you are a leftist, I understand you are probably frustrated the Democrats won’t go further. Look at the big picture. The Democratic Party may not have moved much, but the party moved. It adjusted its agenda in response to inequality and stagnant living standards. The one mistake no voter should make is pretending the two parties are different versions of the same thing.

— David Leonhardt is a columnist with The New York Times.