Scott Walker enters the Republican presidential race with far stronger ties to the party’s biggest fund-raisers than any other candidate besides Jeb Bush.Roughly half of the nation’s top 250 Republican donors have given money to Mr. Walker in his campaigns for Wisconsin governor, according to an Upshot analysis of Federal Election Commission records and state records. By comparison, 30 percent have given to Senator Marco Rubio of Florida, 20 percent to Senator Ted Cruz of Texas and 10 percent to Gov. Chris Christie of New Jersey.A presidential campaign is a chance for candidates to introduce themselves to top fund-raisers, and...