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).
Paul Wellstone
In 1999, Wellstone formed an exploratory committee to run for President of the United States in the 2000 election. After campaigning in the early primary states, he announced he would not seek the presidency because of sustained physical limitations from a college wrestling injury. His condition was later diagnosed as multiple sclerosis. As Senator, Wellstone authored the Wellstone Amendment for the Bipartisan Campaign Reform Act of 2002. His efforts toward campaign finance reform were posthumously overturned in 2010 by the U.S. Supreme Court in "Citizens United v. Federal Election Commission". In 2002, he was the only Senator facing reelection to vote against the congressional authorization for the Iraq War.