Just four short years after John McCain’s politically-motivated selection of Sarah Palin, the Republican Party once again is signaling its lack of enthusiasm for its most logical candidates for vice-president. The potential of Condoleezza Rice has excited some in the party, eager for an unconventional choice even though the former secretary of state supports abortion rights. Others are pushing Florida Sen. Marco Rubio, despite his serving fewer than two years in the Senate.

In fact, if Romney were to pick Rice, Rubio or any of the other non-traditional candidates being considered, it would be the latest signal of the increased importance of diversity in national campaigns and the impending death of a long-time political tradition – the all-white male presidential ticket.  A number of irreversible factors are converging in our nation’s politics and forcing us to redefine what it means for either major party to have a “balanced” presidential ballot. Even if Romney opts for a more traditional candidate, as expected, 2012 may be the last time we see the familiar image of two white men on the ticket of either major party.

Related: Does Romney need to bring diversity in his running mate choice?

For most of recent history, a strong presidential ticket was based primarily on ideological positioning and regional identification.  John F. Kennedy picked Texas’ Lyndon Johnson so he could have a southerner on the ticket in 1960. Ronald Reagan, a conservative hero, tapped the more moderate George H. W. Bush twenty years later.

In recent presidential cycles, the significance of geography has diminished, but candidates have looked for a running mate who balanced the ticket with experience (Dick Cheney in 2000) or youth (Dan Quayle in 1988). Except for Walter Mondale’s selection of Geraldine Ferraro in 1984, every person on the ticket before 2008 had been a white male.

But now, racial and ethnic minorities and women have become an increasingly important part of the electoral landscape. They comprise a growing part of the electorate, as well as many of the media pundits and advisers who shape the political environment.

Obama’s coalition of African-Americans, Hispanics, youth and women, and the historic over-representation of these groups among the electorate, were two of the biggest factors in the president’s electoral success in 2008.  A Pew Research study declared the 2008 electorate the most diverse in history.