WASHINGTON — Last week on Fox News, Senator Tom Cotton, Republican of Arkansas, lamented how it was “very disappointing to see the other party trying to politicize” coronavirus when national unity should be the order of the day. But six years ago, it was a different story when Mr. Cotton, then running for the Senate as Republicans worked to seize the majority, hit the Obama administration for “not protecting our country and our families from Ebola.”

Mr. Cotton was far from the only one.

Republican candidates and their conservative allies pounded Democrats and the Obama White House over their handling of the Ebola crisis in the weeks before the 2014 elections, capitalizing on it as part of an aggressive campaign strategy that ultimately flipped nine Democratic Senate seats and won them the majority they still hold today. Ebola was far from the only issue in that election, but it was an important one, and it came in the pivotal late stage of the campaign as something of an October surprise.

It was a stark example of how a nationwide health crisis and the public anxiety it can provoke can be exploited as powerful political weapons in election years. Now, with the tables turned and a Republican president in the White House, Democrats are working to use the administration’s response to the novel coronavirus to amplify their own campaign messages, and Republicans are quick to charge that they are improperly politicizing the outbreak.

“North Carolinians deserve to know: Will Senator Tillis push for adequate resources for this public health outbreak?” read a statement from the North Carolina Democratic Party circulated on Monday, taking aim at Thom Tillis, a vulnerable incumbent.