Evangelical pastor Tony Campolo issued an endorsement for presidential hopeful Hillary Clinton in an essay published earlier this month.

Campolo served as Bill Clinton's spiritual advisor during his presidency, but said he is vetting Hillary for more than personal reasons.

Beginning with Hillary's tenure as first lady of Arkansas, Campolo said she has demonstrated her administrative abilities and commitment to educational reform. He also cited her experience as senator of New York and Secretary of State as evidence of her ability to work effectively across party lines.

"Hillary... understands how Congress works," Campolo wrote, "a needed skill since legislative gridlock has characterised Washington over the last several years."

Although Clinton is pro-choice, the pastor and author said she has a plan to cut the abortion rate "by at least 50 per cent," and reiterated that the former First Lady of the United States is a "committed Christian." He also countered her vote for the War on Terror by blaming former vice president Dick Cheney's allegations of weapons of mass destruction.

"She learned from that experience, and her future carefulness will keep her from making that kind of mistake again," said Campolo. "She was, however, honest enough to admit that she regretted her vote, and honesty is something we need in Washington."

A tarnish in Bill Clinton's presidency was the Monica Lewinsky scandal and ensuing impeachment, but the pastor commended Hillary for staying with her husband through the storm.

"Hillary Clinton modelled being a faithful wife and a loving, effective mother at a time when we needed such a model," he wrote. "Many people thought, in the midst of a crisis that would have destroyed most marriages, she showed that the promises she made to her husband on their wedding day were binding through better and worse, that she really meant it.

"We need a president who keeps her promises."

Hillary announced her candidacy for president earlier this month.