Twenty-second Amendment to the United States Constitution
Some argue that the 22nd Amendment and 12th Amendment bar any two-term president from later serving as vice president as well as from succeeding to the presidency from any point in the presidential line of succession. Others contend that the original intent of the 12th Amendment concerns qualification for "service" (age, residence, and citizenship), while the 22nd Amendment, concerns qualifications for "election", and thus (strictly applying the text) a former two-term president is still eligible to "serve" as vice president (neither amendment restricts the number of times an individual can be elected to the vice presidency), and then succeed to the presidency to serve out the balance of the term (though prohibited from running for election to an additional term).
Rob Portman
In March 2014, Larry Sabato of the University of Virginia Center for Politics speculated that Portman might run for president in 2016. Sabato forecasted: "[Portman] might have an edge in 2016. Americans tire of their incumbent presidents, and often choose a very different successor with dissimilar characteristics. Portman is all steak and no sizzle." In October 2014, students from the College of William and Mary formed the Draft Rob Portman PAC to encourage Portman to run for president in 2016. However, Portman announced in December 2014 that he would not run for president and would instead seek a second term in the United States Senate.
Portman and Senator Ben Cardin (D-Maryland) proposed the Israel Anti-Boycott Act in late 2018 which would make it illegal for companies to engage in boycotts against Israel. Cardin and Portman have been strongly in promotion of the bill, working to integrate it into larger spending legislation to be signed by President Trump.