And then there were five. The former senator from Virginia and Reagan-era Navy secretary joined four other Democratic presidential candidates yesterday, promising to challenge the “shadow elites” of federal government. Famous for wearing combat boots inside the Capitol, Webb can be politically unpredictable. On Wednesday, for example, the Vietnam veteran and populist hinted at decriminalizing drugs just days after defending the Confederate flag’s heritage. He faces a steep uphill climb but promises to add intrigue — and a frank discussion on drug policy — to the campaign.