DENVER - Democratic White House candidate Barack Obama on Wednesday said rival Hillary Rodham Clinton is too polarizing to win the presidency and she has taken positions shared by President Bush and Republican candidate John McCain for political expediency. Obama depicted Clinton as a calculating, poll-tested divisive figure who will only inspire greater partisan divisions as she sides with Republicans on issues like trade, the role of lobbyists in politics and national security. At the same time, he elevated McCain, fresh off victory in Florida's crucial primary, as the likely Republican nominee. "Democrats will win in November and build a...