a top Republican strategist who asked not to be identified
So, basically, fabricated rumors.
First off, a national campaign is far different than the kind of targeted one-off special election targeting campaigns the Democrats are running now, and like it or not, the sudden shift in the Dems' favor didn't happen until several months in. They elected plurality candidates like Connor Lamb and Doug Jones, when they realized central-office stooges like Jon Ossoff were going to get them nowhere.
Second, after the Dems cleaned up in 2006 and 2012, they have very few opportunities to gain, and plenty to lose.
Still, the Republican Party needs to wake up, find and support candidates the electorate actually wants.