College Park Rally, originally uploaded by Barack Obama.

I grew up in the 1990s loathing Bill Clinton. He and his wife represented everything that was bad about politics — from the corruption and lies they brought from Arkansas to the immoral and embarrassing behavior in the White House. So when some of my conservative friends and colleagues told me they were voting for Hillary Clinton in today’s Virginia primary, I cringed.

One of the best parts of living in Virginia is the ability to cast a vote in either primary — Republican or Democrat. I’ve often found the Democrat races in Northern Virginia far more interesting. Take the contest between Jim Webb and Harris Miller in June 2006. I cast my vote for Miller, even though he was far to the left of Webb. A race between then-Sen. George Allen and Miller would have been far easier for the Republican. Allen might still be a senator had it played out the way I envisioned.

It’s partly for this reason that I decided to cast my vote for Barack Obama today. Although national polls give Obama a small advantage over John McCain in the general election, I firmly believe that McCain would handily defeat the inexperienced Obama. Secondly, I fear what the Clinton attack machine would do to McCain. Their ferocity would be worse than George W. Bush’s ugly attacks in 2000. Anyone who reads this blog regularly knows how much I dislike negative campaigning, and a Clinton-McCain matchup would be just that.

Because my vote for Obama will likely be ridiculed by many friends on the right, I want to explain exactly why I chose to cross party lines to back the Democrat senator from Illinois.

1) Electability. According to Real Clear Politics, McCain would beat Clinton by 1.2 percentage points. McCain, however, loses to Obama by 3.7 percentage points using the same polling average. Despite what these polls indicate today, I predict the numbers would flip once Democrats pick a nominee.

As Clinton pollster Mark Penn told Chris Cillizza, “The Republican attack machine redefines the Democratic candidate.” Fortunately (or unfortunately) for Clinton, there’s nothing left to define. But in the case of Obama, there are millions of Americans who know little about him or his far-left views. His lack of experience makes him even more vulnerable. It is for this reason that I would give McCain the edge in a head-to-head matchup with Obama. I’m not so sure the same is true against Hillary.

Keep in mind that my position has shifted on this matter. Back on Jan. 3, when I called McCain “the man to beat” for his surprise showing in Iowa, I also warned that his emergence could be disastrous for Republicans:

I’m not convinced McCain’s emergence is a good thing for the GOP, especially if Barack Obama wins the Democrat nomination. Unlike a race against Hillary, I’d give the edge to Obama in the general election. It would be the agent of change vs. the agent of old.

2) Not another Clinton presidency. I’ll do whatever it takes to avoid another Clinton in the White House, even if it means crossing over to vote in the Democrat primary, as I did today. The first eight years were bad enough; America can’t afford another Clinton running the country.

I’ve learned firsthand from watching Hillary’s rise in New York in 1999 and 2000 that it’s best to nip these problems in the bud. Had Republicans knocked her out back then, I wouldn’t be writing this today. They failed to do so, and eight years later we’re on the verge of a Clinton presidency.

Even though I’d never consider supporting Obama in the general election, the thought of casting a vote against Clinton was just too tempting.

3) The audacity of hope. Suppose my plan backfires and Obama ends up as the leader of the free world. There are some positive things that could result from the first black president and an inspiring young leader.

America’s image around the world almost certainly increase, giving us a greater ability to fight the war on terror. As much as I admire President Bush for his strong foreign policy, there’s no question our country has suffered as a result of his “You’re either with us or against us” way of thinking. That’s unfair to Bush, but it is reality.

If — and it’s a big if — Obama were to pursue a robust foreign policy with reliable national security advisers, he could make significant strides. I’m less confident of Clinton in this regard based on her husband’s failure to stop Osama bin Laden from building his al Qaeda network in the 1990s; Hillary would almost certainly bring back many of those same advisers. Read the wonderful book, “The Looming Tower,” and you’ll understand exactly why I’m scarred.

And finally, even though I dislike most of Obama’s policies, I do admire his willingness to engage with Republicans. The most notable example came in 2006 when he teamed with conservative Sen. Tom Coburn to pass the Federal Funding Accountability and Transparency Act, a bill that had the backing of the bipartisan coalition known as Porkbusters. I’m much more confident in Obama’s bipartisan spirit than anything Hillary would have to offer.

Agree or disagree, that’s my rationale. I’m anxious to see if my gamble pays off.