I’m proud to have founded the Democrats for Trump movement in 2016. President Trump’s pro-growth policies have revived the stagnating U.S. economy, and he deserves a second term. But to have the best chance of re-election, he should replace Vice President Mike Pence on the ticket with Nikki Haley.

I mean no disrespect for Mr. Pence, who’s loyally served the president and the nation. But he’s given Mr. Trump all the help he can. He inspired his fellow evangelical Christians to take a chance in 2016. But in 2020 they’ll already be repelled by the Democrats’ embrace of infanticide. Mr. Trump’s greater obstacle to re-election comes from politically moderate suburban women, many of whom see him as divisive.

In 2004 Ms. Haley was elected to the South Carolina House, where she served three terms. In 2010 she was elected governor. Her tenure as Mr. Trump’s ambassador to the United Nations was admirable. The political savvy and tough-mindedness she cultivated in South Carolina were on full display on the global stage. Ms. Haley was able to direct sanctions against North Korea through the Security Council, vigorously defend America’s interests in the Middle East, and thoughtfully and effectively navigated the bloated U.N. bureaucracy. Because of this, she was able to earn the respect and gain the confidence of diplomats from all over the globe, while earning praise from Americans at home.

Republican National Committee Chairman Ronna McDaniel recently asked “why are we losing with women?” Mr. Trump has promoted women to the highest echelons of the White House. But elevating energetic and effective leaders like Kellyanne Conway, Hope Hicks and Sarah Huckabee Sanders has earned him scant credit.

It’s too late for Mr. Trump to revamp his political personality. But with the 2016 election in the past, Nikki Haley on the ticket could tamp down the antipathy for Mr. Trump that seems to afflict so many moderate and Republican-leaning women. President Trump needs the prospect of a Vice President Haley to help recapture the White House.