Former president Donald Trump sought to position himself as the Republican Party kingmaker on Saturday, telling party donors he will help them win seats in 2022 congressional elections but shed no new light on whether he will seek a second term in 2024.

Trump played host to a dinner at his Mar-a-Lago Club for Republican National Committee donors who are spending the weekend charting the future course of the party in Palm Beach, Florida.

“We are gathered tonight to...