Larry Hogan, the former governor of Maryland and a moderate Republican who has been critical of Donald Trump, stepped down last month from the leadership of the third-party movement No Labels, a move that could signal his preparations to run for president using the group’s ballot line. Hogan did not address his own future in a letter to No Labels President and CEO Nancy Jacobson announcing his resignation as co-chair, but he offered no criticism of the group, its plans or leadership.