BOSTON—President Barack Obama was trying to help Massachusetts Gov. Deval Patrick win re-election on Saturday, but more important to his own political future, maintain a Democratic Senate. After a Patrick rally at the Hynes Convention Center, the president was traveling to West Newton for a fundraiser at the home of Caritas Cristi CEO Ralph de la Torre. The event was expected to raise $500,000 for the Democratic Senatorial Campaign Committee. It is charged with electing party members to the U.S. Senate. Obama wants to maintain a Democratic Senate to pass the remainder of his first-term agenda. Both it and a...