By APRIL CASTRO Associated Press Veteran Democratic U.S. Rep. Martin Frost will announce plans Friday to challenge Republican incumbent Rep. Pete Sessions in a bid to preserve his congressional career. Frost's current district in the Dallas-Fort Worth area was dismantled by GOP map-drawers earlier this year who were looking to put more Republican Texans in Congress. A Democratic strategist confirmed reports, on condition of anonymity, that Frost will file to run in Congressional District 32. Reports were first published Thursday in The Dallas Morning News. The district encompasses part of north and west Dallas, the largely Hispanic neighborhoods of North...