This year’s U.S. Senate races have produced plenty of memorable debates. One of my personal favorites came a couple of weeks ago in Iowa, when Theresa Greenfield (D) faced incumbent Sen. Joni Ernst (R) in a debate, and both were presented with an agricultural pop quiz. Greenfield aced the test; Ernst did not.

But perhaps even more dramatic was a debate in Georgia this week, in which Jon Ossoff (D) humiliated incumbent Sen. David Perdue (R) — more than once. The two were scheduled to meet again for another debate last night, but that didn’t happen.

Ossoff tweeted that Perdue cancelled their final debate, adding that at last night’s debate Perdue had, “no answers when I called him out on his record of blatant corruption, widespread disease, and economic devastation.” Perdue’s spokesman John Burke confirms that the incumbent senator did cancel the debate, but says it’s because President Donald Trump will be in the state campaigning and Perdue intends to be by his side.

Sure. Whatever you guys say.

What’s just as notable, however, is the familiarity of these circumstances. In Mississippi’s U.S. Senate race, incumbent Sen. Cindy Hyde-Smith (R) declared two weeks ago that she won’t debate former Agriculture Secretary Mike Espy (D). “The only people interested in debates are reporters and losing candidates,” the Republican argued.

In Alabama, incumbent Sen. Doug Jones (D) has said he’s eager to debate Tommy Tuberville (R), a former college football coach and failed hedge-fund manager, but the Republican challenger has refused to share a stage with the senator. (Tuberville has also avoided questions from journalists and generally avoids public appearances. He’s favored to win anyway.)

In Louisiana, incumbent Sen. Bill Cassidy (R), at least as of a few days ago, ruled out debating Shreveport Mayor Adrian Perkins (D), too.

And in Michigan, incumbent Sen. Gary Peters (D) has offered to debate challenger John James (R), but the Republican’s campaign has raised concerns about the terms and proposed formats.

For many of these candidates, the calculus is simple: would participating in a debate make them appear worse than refusing to debate? The answer is apparently obvious. Just as Georgia’s David Perdue.

Update: While we’re on the subject, it’s also worth noting that in Kansas’ surprisingly competitive U.S. Senate race, Rep. Roger Marshall (R) was invited to participate in a debate in Topeka this week, but he refused to show up. When the Republican congressman said he didn’t know about the event, the local NBC News affiliate, KSNT, literally brought the receipts to refute his claims.

Second Update: A reader emails to remind me that Sen. Lindsey Graham (R-S.C.) recently skipped a debate, too.