WASHINGTON: Finally Democratic presidential hopeful Barack Obama chose Sen. Joseph Biden, a Delaware Democrat, to be his vice presidential running mate, selecting one of the party’s leading foreign-policy figures and harshest critics of Republican John McCain’s national security views. The Obama campaign sent a text message to supporters at about 3 a.m. EST, announcing the decision.

The choice of Biden, 65, is aimed at addressing questions about Obama’s inexperience in international affairs, his biggest vulnerability against McCain. Biden has led the attacks on the Republican candidate, assailing McCain for supporting President George W. Bush’s policies, including his argument that Iraq is the main front in the battle against terrorists.

At a July 14 news conference in Washington, Biden criticized McCain for considering Iraq as America’s central concern in the war on terror. “Yet it’s Afghanistan,” he said. “And John’s policy in Iraq prevents us from having a larger strategy to deal with that.”

What else does Biden bring to the ticket? Insiders say he has a love of politics and public service. He never tried to get rich from his role, even though he has been in the Senate for decades (a convenient thing when you’re making fun of “houses-by-the-dozen John McCain”), and he knows how to reach out to blue-collar voters.

Biden is the son of a car salesman who takes the train home to Wilmington — about a two-hour ride — almost every night. His personal story is compelling: a riches-to-rags family background; a first wife and daughter killed in a car crash; a devoted life with his second wife; a bunch of grandchildren whom he adores as much as they adore him.

He has never had a hint of financial or sexual scandal.

And, significantly, Biden is a Catholic — a demographic must for a Democratic ticket eager to get swing voters in heavily Catholic states such as Pennsylvania and Ohio.

Another advantage: Biden has few enemies among Democrats and even most Republicans like him.

Political insiders here say Biden does bring risks to the table: He can’t keep his mouth shut and sometimes he talks before thinking.

He loves to hear himself talk. He can get carried away with his enthusiasm. And he loves the spotlight.

McCain’s team was ready for Obama’s announcement. By 6 a.m. yesterday, just hours after news broke that Obama picked Biden as his Democratic ticket running mate, McCain’s campaign released a critical ad featuring the Delaware senator.

The speed with which the campaign was able to get the ad to the media has already proved beneficial.

During CNN morning broadcast, anchor Betty Nguyen marveled at how quickly the McCain campaign produced the ad and said they “brought (a copy) to our doorstep very early this morning.” The cable network then proceeded to play the advertisement in its entirety on its news broadcast.

Up next on the Republican fight list: Surrogates who were prepped last week on the possibility of a Biden pick, will be dispatched throughout the day.

McCain, who is vacationing at home in Arizona and preparing for the Republican convention, will call Biden to congratulate him, according to a McCain staffer.

The Democratic National Convention begins tomorrow in Denver, Colorado.