In 2008, Catsimatidis became engaged in efforts to take over SemGroup LP, a bankrupt oil, gas, and asphalt trading, storage and transportation company, headquartered in Tulsa, Oklahoma. Catsimatidis gained control over a majority of the company's management committee, but his efforts were met by opposition from the company's existing management, who argued for selling off at least some of the company's assets, while Catsimatidis wanted to keep the company together. In February 2009, Catsimatidis was sued by a group of SemGroup executives, who sought the removal of Catsimatidis and his allies from the committee. In July Catsimatidis reached a settlement with SemGroup, pursuant to which he acquired a piece of SemGroup's asphalt business and dropped his competing plan for the company's proposed reorganization.
In 2008, Catsimatidis was widely viewed as a potential mayoral candidate, along with City Council Speaker Christine Quinn, Representative Anthony Weiner, businessman Richard Parsons, Police Commissioner Raymond Kelly, City Comptroller Bill Thompson (the eventual Democratic nominee), and state Senator Martin Golden. By July 2008, Catsimatidis formed an exploratory committee of advisors and operatives, including Robert Ryan, Alan Bernikow, Lawrence Mandelker, and Jose Ithier. McLaughlin & Associates was the committee's polling firm.