Sen. John McCain (R) has known from an early stage that he could face a tough primary in his bid for re-election this year, and acted on it. He already launched radio ads touting his effort to block President Obama's "extreme left wing crusade." And just this week, Sen.-elect Scott Brown (R) recorded robocalls that went out to voters in Arizona. Now, a Rasmussen poll (502 LVs, 1/20, MoE +/- 4.5%) shows the Maverick just over 50 percent in a potential matchup against former Rep. JD Hayworth -- not the best position for an incumbent to be, but an improvement...