BY STEVEN THOMMA
Barack Obama chose safe rather than bold, experience rather than change.
With his long record, Delaware Sen. Joe Biden will help assure some voters nervous about Obama's lack of experience on foreign affairs, much as Dick Cheney did when he was chosen as the young George W. Bush's running mate.
And yet, Biden showed immediately he is willing to take on the traditional attack-dog role of a running mate, skewering John McCain as too rich to relate to the problems of average Americans.
''Biden can probably take apart anybody that McCain chooses, and do it with a sti-letto and a smile,'' said Sherry Bebitch Jeffe, a political scientist at the University of Southern California.
That remains to be seen.
One of the Senate's least well off, Biden could help Obama reach out to working-class voters who've been cool to the candidate in places such as Ohio and West Virginia.
And as a Roman Catholic, he could speak to that swing voting bloc in key states such as Florida, Pennsylvania and Wisconsin.
''For decades he has brought change to Washington, but Washington hasn't changed him,'' Obama told a crowd Saturday in Springfield, Ill., where he introduced his new running mate.
``He's an expert on foreign policy whose heart and values are firmly rooted in the middle class. He has stared down dictators and spoken out for American cops and firefighters.''
Overall, Biden looks familiar and safe as Obama's choice for vice president on the Democratic ticket. That may undercut Obama's message of bold new leadership.
But it also could help Obama look careful and deliberate at the very time Republicans want to cast him as a dangerous, radical neophyte.
A MIXED BAG?
''It's safe but not exciting,'' said Susan MacManus, a political scientist at the University of South Florida.
A bold choice, a real Washington outsider such as Virginia Gov. Tim Kaine or Kansas Gov. Kathleen Sebelius, would have put a punctuation mark behind Obama's promise to change Washington and American politics.
Biden? ''I don't think it helps the change message,'' said Steven Schier, a political scientist at Carleton College in Minnesota.
That may not be all bad, especially at a time when Russian tanks have been on the roll in Georgia and Pakistan is changing leaders.
Obama needs to assure voters that he can handle a crisis, the same concern that former Democratic rival Hillary Clinton raised when she aired an ad asking who voters want in the White House when a crisis erupts at 3 a.m.
A recent Zogby poll found, for example, that voters prefer McCain to handle those issues. Obama also wants to attract more support from Roman Catholics, a key swing group closely divided between McCain and Obama.
Catholics make up about one out of four voters nationwide, and a higher concentration in such political battleground states as Florida, New Hampshire, New Mexico, Pennsylvania and Wisconsin.
And Biden -- son of blue-collar workers and a man whose net worth of less than $150,000 is well below that of many Senate members -- can speak to white, working-class voters in a way that Obama might not.
In their Illinois appearance, Obama emphasized Biden's dedication as a new senator to his two sons after their mother's death in a car accident 35 years ago.
''He never moved to Washington,'' Obama said. ''Instead, night after night, week after week, year after year, he returned home to Wilmington on a lonely Amtrak train when his Senate business was done. He raised his boys -- first as a single dad, then alongside his wonderful wife, Jill.'' The couple also have a grown daughter.
Beyond those niche appeals, Biden likely will do well in one of the key roles for a running mate -- attacking the other ticket.
In his joint appearance with Obama on Saturday, he went after McCain, a longtime personal friend, as having given ``into the right wing of his party and yielded to the very Swift Boat politics he once so deplored.''
He also said McCain would continue President Bush's policies. And he chided that McCain is so wealthy and insulated from average people's concerns that his version of making difficult kitchen-table decisions is that ``he'll have to figure out which of his seven kitchen tables to sit at.''
''He is a tough attack dog,'' said Sherry Bebitch Jeffe, the USC political scientist.
Biden does carry some risks.
First, of course, is his image as an insider. Second is a tendency to make off-the-cuff remarks that can appear impolitic, such as calling Obama the first ''clean'' black candidate for president or noting how Indians fill all the jobs at Dunkin' Donuts.
The Obama campaign could try to massage both flaws.
Already Saturday, for example, campaign aides were stressing how Biden rides the train home to Delaware from Washington every day to live with his family.
She suggested the campaign would also attempt to paint his tendency for blunt, sometimes embarrassing comments as a penchant for being candid and honest.
''That could position him as a maverick,'' Jeffe said. ``For the average voter, it could be a positive. It takes him out of the stereotype of the smooth, Washington insider.''
One that will be harder to counter is the record of criticisms Biden leveled at Obama during the primaries. In one, for example, Biden called Obama too inexperienced, a clip the McCain camp rushed into TV commercials by midday Saturday.
McClatchy correspondent Margaret Talev contributed to this report from Springfield, Ill.