The political network backed by the Koch brothers, already spending tens of millions of dollars this year to boost Republicans' chances of retaking the Senate, is expanding its national playbook as part of a long-term strategy designed to strengthen conservatives heading into the 2016 presidential campaign. The effort, part of an overall budget that organizers expect to total nearly $300 million this year, includes broadening outreach to veterans, viewed as an energized constituency in the wake of the recent Veterans Affairs scandal, and messages tailored for Latinos and young people, long considered core Democratic constituencies. The strategy for 2014 includes a new super PAC that can pour all its money into overt election activity. The plan underscores the huge reach of the Koch-backed operation, a singular force in American politics that has functioned outside the traditional campaign finance system. The Koch-backed network, a coalition of nonprofit organizations not required to disclose their donors, raised $407 million in the 2012 cycle, a presidential election year in which outside spending increased greatly on both sides of the aisle. This year, the network is likely to outstrip other organizations on both the left and the right with spending on television ads and on-the-ground organizing. Its main political organ, the free-market advocacy group Americans for Prosperity, has 240 full-time employees in 32 states, more than double the size of its 2012 staff.