Grenier ran for the United States Senate in 1966 against John Sparkman.[4] Grenier only won 39 percent of the vote but it was the highest percentage of the vote that anybody had won against Sparkman in Sparkman's Senate career.
Grenier was also involved in campaign of Alabama Republican Guy Hunt and the controversies which followed Hunt during his term in office.
Grenier also worked as a litigator for Lange Simpson Robinson and Somerville, one of the oldest and most distinguished law firms in Birmingham, Alabama, for many years.
Grenier died of lung cancer on November 6, 2007, in a hospital in Houston, Texas aged 77.