The biggest donors in the Republican Party are financing a new group to recruit seasoned candidates and protect Senate incumbents from challenges by far-right conservatives and Tea Party enthusiasts who Republican leaders worry could complicate the party’s efforts to win control of the Senate. The group, the Conservative Victory Project, is intended to counter other organizations that have helped defeat establishment Republican candidates over the last two election cycles. It is the most robust attempt yet by Republicans to impose a new sense of discipline on the party, particularly in primary races. “There is a broad concern about having blown...