WASHINGTON -- Senator John F. Kerry, laboring to achieve a foreign policy victory that would be a highlight of his career, gained crucial support yesterday for a nuclear arms control treaty with Russia from his Massachusetts colleague, Republican Senator Scott Brown. Brown's backing gave Kerry additional momentum heading into a possible vote today. As chairman of the Senate Foreign Relations Committee, Kerry is President Obama's man in charge of trying to lock down the two-thirds support of the Senate -- 67 votes if every members shows up — required to ratify the New START pact. Kerry and other senators have...