Article II of the US Constitution:
http://www.law.cornell.edu/constitution/constitution.articleii.html#section1http://www.law.cornell.edu/constitution/constitution.amendmentxii.html"Each state shall appoint,
in such manner as the Legislature thereof may direct, a number of electors, equal to the whole number of Senators and Representatives to which the State may be entitled in the Congress: but no Senator or Representative, or person holding an office of trust or profit under the United States, shall be appointed an elector.
...
The Congress may determine the time of choosing the electors, and the day on which they shall give their votes; which day shall be the same throughout the United States."
We currently have the Electoral College, described in detail in Article II, Section I, and further elaborated in Amendment XII. Each state gets to decide how to chose its electors. It just so happens that so far, every state has held a popular election to determine its electors. When you vote for president, you are not actually voting for that candidate, rather you are voting for your electors, who will then cast their votes on your behalf.
The XV, XIX, and XXVI amendments don't guarantee anyone the right to actually vote for president. They merely state that states cannot deny anyone over the age of 18 the right to vote based on race or gender.
http://www.law.cornell.edu/constitution/constitution.amendmentxv.htmlhttp://www.law.cornell.edu/constitution/constitution.amendmentxix.htmlhttp://www.law.cornell.edu/constitution/constitution.amendmentxxvi.htmlNote also that the Poll Tax amendment (XXIV) states:
The right of citizens of the United States to vote in any primary or other election for President or Vice President, for electors for President or Vice President, or for Senator or Representative in Congress, shall not be denied or abridged by the United States or any state by reason of failure to pay any poll tax or other tax. Note that even here, it specifies voting for
electors for President and VP, not actually direct votes.
http://www.law.cornell.edu/constitution/constitution.amendmentxxiv.htmlI am not defending this practice, but I'm merely stating the facts. There is an incorrect assumption among many that there is a constitutional right to vote for President, when that just doesn't exist. In order to accomplish that, we would need to pass a new amendment abolishing the Electoral College, and institute a direct popular vote.