EXCLUSIVE: Sen. Barack Obama will portray himself Thursday night as an agent of change for mainstream America, but his eight-year voting record in the Illinois Senate shows the Democrat was on occasion an agent of isolation who took stands - particularly on anti-crime legislation - that put him to the left of his own party. Mr. Obama was the only member of the state Senate to vote against a bill to prohibit the early release of convicted criminal sexual abusers; was among only four who voted against bills to toughen criminal sentences and to increase penalties for "gangbangers" and dealers...