Sembler was the chairman of the Scooter Libby Legal Defense Trust,[2] and was a co-chair of the Florida Finance Committee for Mitt Romney.

[9] On October 11, 2011, Republican presidential hopeful Mitt Romney announced that he had appointed Sembler to his Florida Finance Team.

On 26 April 2016, he pledged to begin a fundraising drive to defeat the proposed constitutional amendment in Florida that would legalize medical marijuana.

The Sembler Company came to the attention of federal investigators in 2008 after a planned shopping center in Boynton Beach, Florida, that had previously been denied a zoning variance, was suddenly approved after a payment of $100,000 had been made to lobbyist Hugo Unruh.

[12] In February 1989, President George H. W. Bush appointed Sembler United States Ambassador to Australia and Nauru, where he served for three and a half years.

On August 23, 1989, cartoonist Garry Trudeau published a Doonesbury comic strip which seemed to imply that Sembler had purchased the ambassadorship.

[13][14] It has been pointed out that Sembler had no previous diplomatic experience and had donated $100,000 to the presidential campaign of George H. W. Bush shortly before his appointment.

[18] President George W. Bush appointed Sembler to serve on the Honorary Delegation to accompany him to Jerusalem for the celebration of the 60th anniversary of the State of Israel in May 2008.

In 1976, Sembler and his wife, Betty, founded Straight, Incorporated, an adolescent drug treatment program which has treated more than 12,000 young people who were labeled as addicts.