Democrats’ meddling in GOP primaries paid dividends after the party swept races in which it had backed pro-Trump candidates this year, figuring those contenders would be easier to beat in the general elections.
Democrats spent more than $40 million boosting six Republicans who vocally supported Mr. Trump or got his endorsement. All those candidates lost, including New Hampshire Senate candidate Don Bolduc, who could not beat vulnerable Democratic Sen. Maggie Hassan.
The Democrat-aligned Senate Majority PAC spent $3.5 million attacking Mr. Bolduc’s primary foe, Chuck Morse, the GOP establishment’s preferred candidate, according to a Fox News rundown.
Democrats also propped up Republican Bob Burns, who lost to Democratic Rep. Annie Kuster in New Hampshire.
They also bolstered Republican John Gibbs, who beat Rep. Peter Meijer in the GOP primary after Mr. Trump attacked Mr. Meijer for voting to impeach him. Mr. Gibbs went on to lose to Democrat Hillary Scholten.
The Democratic PACs’ decision to step into the GOP primaries was viewed by some Democrats as uncouth and potentially risky. They feared Trump-backed candidates viewed as zany or less preferable to moderates might actually win as part of a red wave.
The wave didn’t materialize, even if the GOP is on track to retake the House, and Democratic operatives are feeling vindicated over the unorthodox strategy.
Democratic committees ran primary ads to prop up three Republican gubernatorial candidates — Dan Cox in Maryland, Darren Bailey in Illinois and Doug Mastriano in Pennsylvania — who later lost to Democrats in the general contests.