WASHINGTON, Aug. 18 — Senator John McCain is locking up a cast of top-shelf Republican strategists, policy experts, fund-raisers and donors, in a methodical effort to build a 2008 presidential campaign machine, drawing supporters of President Bush despite the sometimes rocky history between the two men. Mr. McCain’s effort to woo a diverse lineup of backers and scare off rivals has augmented his travel schedule on behalf of Republicans — which this week and next includes trips to Iowa, Louisiana, Virginia, South Carolina, Ohio and Florida. The effort is fueling a fund-raising operation that has helped him build loyalty throughout...