Hillary Clinton and John McCain both paid tribute to Martin Luther King Jr. on Friday by visiting the Lorraine Motel in Memphis, the site of King's assassination exactly 40 years earlier.

Which makes me wonder: Would the two senators have gone to the motel had they not been running for president?

If the answer is no, then their visits to the spot where King was gunned down were the worst kind of political opportunism.

Ironically, presidential candidate Barack Obama - an African-American whose run for the White House might not have been possible without King's efforts four decades ago - didn't go to Memphis on Friday. Perhaps he realized his candidacy itself said more about his gratitude for the civil rights leader than a cheap photo op ever could.