Twenty-second Amendment to the United States Constitution
As worded, the primary focus of the 22nd Amendment is on limiting individuals twice elected to the presidency from being elected again. Due to this, several issues could be raised regarding the amendment's meaning and application, especially in relation to the 12th Amendment, ratified in 1804, which states, "But no person constitutionally ineligible to the office of President shall be eligible to that of Vice-President of the United States". While it is clear that under the 12th Amendment the original constitutional qualifications of age, citizenship, and residency apply to both the president and vice president, it is unclear whether someone who is ineligible to be elected president could be elected vice president. Because of this apparent ambiguity, there may be a loophole in the 22nd Amendment whereby a two-term former-president could be elected vice president and then succeed to the presidency as a result of the incumbent's death, resignation, or removal from office (or even succeed to the presidency from some other stated office in the presidential line of succession).
Primary elections in the United States
In California, under Proposition 14 (Top Two Candidates Open Primary Act), a voter-approved referendum, in all races "except" for that for U.S. President and county central committee offices, all candidates running in a primary election regardless of party will appear on a single primary election ballot and voters may vote for any candidate, with the top two vote-getters overall moving on to the general election regardless of party. The effect of this is that it will be possible for two Republicans or two Democrats to compete against each other in a general election if those candidates receive the most primary-election support.