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For much of the past six weeks, political campaigns were reluctant to focus too heavily on the coronavirus outbreak. Though some outside groups started to criticize President Trump’s handling of the crisis, the virus was largely considered off-limits to many campaigns, which worried about politicizing the unending tragedy.

That, however, has changed.

Now, more than 50 percent of all political ads on TV are about the coronavirus, the first time that a majority of ads were focused on the outbreak, according to Advertising Analytics, an ad tracking firm. There were 33 unique ads centering on the virus that aired last week, spanning the presidential, Senate and congressional elections.

Of course, some groups have been advertising about the pandemic for weeks. But five weeks ago, as states like New York, New Jersey and California shuttered schools and announced stay-at-home orders, less than 2 percent of ads touched on the coronavirus. Now, 54 percent are about the coronavirus.

For Democratic candidates and liberal-leaning groups, one issue has dominated recent ads: the lack of personal protective equipment — commonly referred to as P.P.E. — for front-line medical workers. Those ads have characterized the shortage as a failure of the Trump administration.