The safest Democratic congressional seat in the country right now is Rep. José E. Serrano's New York district in the South Bronx. In the past 10 elections, the “worst” performance by a Democrat has been winning this district with 66 percent of the vote.

Serrano's district may be the extreme example of the kinds of districts the 60-some House Democrats who are skipping Donald Trump's inauguration represent. But it's not an anomaly.

The Democrats who won't be there Friday come from some of the most Democratic districts in the country. At least 15 lawmakers who represent 26 of the most Democratic districts in the country, as ranked by the Cook Partisan Voting Index (a measure of a district's partisanship as compared to the nation), aren't attending.

This is not a coincidence. These Democrats making the ultimate partisan statement aren't likely to face much blowback from constituents — they hail from some of the most partisan districts in the country.

In many of these safe Democratic districts, electoral danger lurks not in the form of a Republican (Serrano's GOP challenger got just 3.5 percent of the vote in November) but the possibility of a primary challenger from the left.

Skipping out on the inauguration of one of the most controversial presidents in modern history is one way to signal your progressive bona fides, said Matt Green, a political science professor at Catholic University.

“They might be thinking,” Green said, "'Do I want to be challenged in a primary by someone who says: Your representative went to Trump's inauguration, even after he insulted John Lewis'? Whether that's fair or unfair, that's one attack ad you don't want to have in 2018.”

Lawmakers have skipped inaugurations before, say historians. Rep. John Lewis (D-Ga.), whose decision to boycott Trump's inauguration — along with Trump's aggressive Twitter response — inspired many other Democratic lawmakers to follow his lead, didn't attend the 2001 inauguration of President George W. Bush either.

But to have this many lawmakers skip an inauguration — and to have them declare it as publicly as possible — is highly unusual. And it's not just the fact that they're doing it — it's the way they're doing it, too. To wit:

  • “I’m just not a big Trump fan,” Rep. Kurt Schrader (D-Ore.) told Oregon Public Broadcasting. “He hasn’t proved himself to me at all yet, so I respectfully decline to freeze my ass out there in the cold for his particular ceremony.”
  • “When you're getting up in the middle of the night and tweeting about 'Saturday Night Live' and Meryl Streep and you're insulting the head of the CIA and people like John Lewis,” Rep. John Yarmuth (Ky.) told me, “you're diminishing the office, you're acting like a child, and if you're going to be president of the United States, you have to maintain the dignity of that office.”

That's one way to fly your liberal flag.

Here's another: At least one Democrat who has decided to attend Trump's inauguration apparently felt the need to rationalize her decision with an ultimate-partisan explanation. Rep. Gwen Moore (D-Wis.), who represents a safe Democratic district, said in a statement Wednesday: “As a proud Democrat, I want President-elect Trump to see me front and center as he’s sworn in. I want him to see exactly what his opposition looks like. When he sees me, I want him to see The Resistance.”

The lawmakers who are boycotting say they don't want to normalize Trump's behavior. Critics, of course, say their absence could help normalize a future where elected officials regularly skip one of the most visually symbolic ceremonies for U.S. democracy.

“The big question now is,” Green said, “whether this becomes an expectation going forward that people of the opposite party of the president-elect don't go to the inauguration.”

It's a fair question. This isn't the first presidential election where a member of the opposition party has questioned a president's legitimacy. We live in a world where states are drawing congressional districts to be more — not less — partisan, which in turn forces lawmakers to move to the poles of their party to stay alive politically. It's not too hard to imagine that skipping out on a new president's inauguration could become a marker of your dedication to your own party.

These lawmakers' reelections aside, political scientists say that would be one of the most lasting impacts of Friday. “That's just be one more step away from unity and toward party polarization,” Green said. "[To] those of us who worry about this stuff, that's disconcerting.”