(UPDATED with Vice President Biden's statement below.)

So maybe there was some truth to this after all.

In an e-mail to supporters this morning, Delaware Attorney General Beau Biden announces that he will run for re-election in 2010, and not seek his father's former Senate seat as had long been expected. From the e-mail:

As many of you know, since returning home from Iraq, I have been giving serious consideration to running for the United States Senate. I have received strong encouragement both here in Delaware and all across the country to undertake this effort - and this outpouring of support has truly been humbling.

I understand why people care so deeply about this election. The challenges we're facing as a country are extraordinarily difficult. The economy. Jobs. Health care. Energy. Education. Climate change. Financial regulation. Foreign policy. These are not only the issues of the moment - they're the issues that will determine our children's future. And as someone who has had the privilege of serving with the bravest men and women on this planet, I care deeply about how we treat our returning veterans and how we resolve our involvement in Iraq and Afghanistan.

I feel strongly about these issues. However, my first responsibilities are here in Delaware. I have a duty to fulfill as Attorney General - and the immediate need to focus on a case of great consequence. And that is what I must do. Therefore I cannot and will not run for the United States Senate in 2010. I will run for reelection as Attorney General.

This can only be seen as a major blow to Democrats' chances not just of holding this seat, but holding onto its increasingly precarious majorities in Congress. You can just imagine the conversations Democratic incumbents and potential recruits are having with their staff, and themselves: "Well, if the Vice President's son doesn't want to run, what does that say about the environment?" The symbolism of Democrats potentially losing Vice President Biden's seat, when the seats of President Obama and Senate Majority Leader Harry Reid are also at risk, is also troubling for Democrats.

Biden's decision not to run will have many questioning yet another appointment made in late 2008. Then-Gov. Ruth Ann Minner (D), a close ally of Vice President Biden, chose longtime Biden aide Ted Kaufman to fill the seat with the idea of keeping it warm for Beau Biden, who was en route to Iraq at the time. Former Lt. Gov. John Carney (D) had been lobbying for the appointment, and would have certainly run again in 2010 as the incumbent. Now, Democrats have no clear favorite, while Republicans have a strong candidate in Rep. Mike Castle.

One potential candidate for Democrats is New Castle County Exec. Chris Coons. Carney, who had decided to run for the U.S. House, could still potentially switch races at this point. Calls to aides for Beau Biden and Carney were not immediately returned.

UPDATE: Vice President Biden released this statement about his son's decision:

"I know I sound like the proud father I am, but all of his life, Beau has put duty above any personal ambition, and this decision today is another example of that exceptional character trait. Jill and I are so proud of our son and feel fortunate as Delawareans that he is our Attorney General."