Once partners together in a bid to reshape the federal judiciary and build a conservative Supreme Court majority, former President Donald Trump and Senate Minority Leader Mitch McConnell are now in a battle for control of the Republican Party.

Republican insiders are unsure which side will prevail. Some think Trump’s presidency was a sign rank-and-file voters have turned against GOP establishment politics for the foreseeable future. Others doubt the ex-president has the attention span or organization to compete with the wily Senate tactician from Kentucky.