The landscape confronted by a candidate setting off on the final stretch of a long political campaign is a treacherous one these days, where it's impossible to anticipate and avoid every landmine.

Given the political realities of this national election, Barack Obama, due tonight to accept the Democratic nomination for the presidency, made a well-reasoned choice in the selection of his running mate: Joe Biden, his colleague in the U.S. Senate.

That choice came with risks.

Obama supporters who are less than enthused with the selection worry that Biden, notorious as a bit of a bulldog, may derail the sense of unity that the man at the top of the ticket seeks to convey.

Judging by last night's passionate and pointed keynote speech, the senior senator seems willing to go on the offensive for the team, and he pulls no punches.

But other strategists rightly note that this is a necessary tactical step if the Democrats intend to meet the Republicans' already aggressive challenge head-on.

In addition, some of Obama's fans as well as his critics see the selection as an acknowledgment that the Illinois senator needs the backing of an older, more experienced Capitol veteran. Tapping Biden seemed an attempt to balance the ticket to offset perceptions that Obama lacks the foreign-policy credentials of a commander in chief.

Whether or not the perception is correct, it's clear that to anyone with a grasp of realpolitik that in the realm of American national campaigns, perceptions must be addressed. As chairman of the Senate Foreign Relations Committee on which Obama also served, Biden's experience is a palpable advantage, especially given the national unease over Russia's invasion of the Georgian republic and ongoing uncertainty over Iraq and Iran.

Despite the brickbats Biden threw Obama's way as he pursued the presidential nomination for himself, the two senators have a collegial working relationship. Even if they haven't always seen eye-to-eye on the Iraq conflict, observers of the foreign relations panel noted Obama's willingness to listen and learn, and his ability to contribute his own astute perspectives.

That suggests a foundation for cooperation exists that could help fuel the campaign team through the challenging months ahead.

In addition, Biden's blue-collar upbringing (he's still known as the "Amtrak senator," commuting home to Delaware on weekends) helps to blunt charges that the Democrats — Obama, in particular — are elitists.

Those familiar with the Hawai'i-born senator's own humble roots, being raised by a single mom and by grandparents, know that perception is flat-out wrong. But it still needs to be addressed in the context of a national campaign.

Finding the right mix of discretion and assertiveness will take a balanced touch. But what candidate Obama needs most is to move forcefully from lofty rhetoric to the specifics of plans grounded in experience. His running mate seems capable of providing just that kind of support.