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).
2020 United States presidential election
Beginning in August 2017, reports arose that members of the Republican Party were preparing a "shadow campaign" against Trump, particularly from the moderate or establishment wings of the party. Now late Arizona Senator John McCain said that "[Republicans] see weakness in this president." Maine Senator Susan Collins, Kentucky Senator Rand Paul, and former New Jersey Governor Chris Christie all expressed doubts in 2017 that Trump will be the 2020 nominee, with Collins stating "it's too difficult to say." Senator Jeff Flake claimed in 2017 that Trump is "inviting" a primary challenger by the way he is governing. Longtime political strategist Roger Stone, however, predicted in May 2018 that Trump may not seek a second term if he succeeds in keeping all of his campaign promises and "makes America great again".