Former Vice President Mike Pence is expected to soon declare a long-shot campaign for the White House against the president under whom he served, pitching himself as a “classical conservative” who would return the Republican Party to its pre-Trump roots, according to people close to Mr. Pence.
Mr. Pence is working to carve out space in the Republican primary field by appealing to evangelicals, adopting a hard-line position in support of a…