The only thing we know for sure about the outcome of this year's nail-biting presidential election is that we'll be sending a sitting U.S. senator to the White House for the first time in nearly half a century.

All of the surviving candidates — Republican John McCain and Democrats Barack Obama and Hillary Clinton — currently serve in the Senate, which has seldom been a place Americans look for executive leadership.

While it seems that half the Senate runs for president every four years, the last sitting senator elected to the White House was John F. Kennedy in 1960.

Warren G. Harding in 1920 was the only other president elected straight from the Senate in the last century, and before that you have to go back to Benjamin Harrison in 1888.

Harry Truman, Lyndon Johnson and Richard Nixon all served time in the Senate, but they passed through the vice presidency on their way to the White House. Truman and Johnson inherited the top job when the presidents they served died in office.

It's difficult to isolate a single reason why senators fare so poorly as presidential candidates. Lack of administrative experience is probably part of it, and let's face it, the thing senators are seen doing most is talking, and the longer they serve, the more they risk coming across as blowhards.

The statehouse has been the better ticket to the White House; four of our past five presidents have been former governors able to sell themselves as fresh faces uncorrupted by Washington.

With voters placing so little value on senatorial experience in choosing presidents, it's ironic that senatorial experience has emerged as a top issue among candidates this year.

Clinton has hammered Obama with her supposed experience as she tries to mount a comeback — most recently in a TV commercial asking voters which of the two they'd rather have answer the White House phone at 3 a.m. in a foreign policy crisis.

But Obama and others are starting to challenge Clinton's claims of vast experience.

Clinton is still a relatively junior senator herself, with seven years of service compared with three years for Obama, who also claims experience from the Illinois Legislature. McCain beats them both with 21 years in the Senate and four years in the House.

On foreign policy, Clinton sits on the Armed Services Committee along with McCain, who is the ranking Republican. Obama sits on the Foreign Relations Committee. None of the three has direct responsibility for the actual conduct of foreign policy.

Clinton was first lady during the eight years her husband Bill Clinton occupied the White House, but does that count as personal executive experience for her? No other first lady has ever made such a claim.

Obama, who at 46 is three years older than Kennedy when he was elected, invites comparisons to the charismatic JFK, and plays his relative lack of Senate experience as an asset, saying, "I haven't spent a lot of time learning the ways of Washington, but I've been there long enough to know that the ways of Washington must change."

If Obama wins the Democratic nomination, his strategy will remain the same as McCain inevitably keeps up the attacks on his few years in the Senate.

If Clinton is the nominee, she'll have to find a new strategy as McCain, by far the more seasoned senator, will make the same inexperience arguments against her that she's made against Obama.

It'll be interesting to hear how she answers her own question about who's more prepared to answer the phone in a crisis.

David Shapiro, a veteran Hawai'i journalist, can be reached by e-mail at dave@volcanicash.net. His columns are archived at www.volcanicash.net. Read his daily blog at blogs.honoluluadvertiser.com.