If you’re looking for signs that Wisconsin Gov. Scott Walker is serious about seeking the 2016 Republican presidential nomination, you could do worse than his appearance this past weekend on Fox News Sunday, in which Walker slogged through what has become a rite of passage for GOP White House aspirants: the rightward lurch/mea culpa on immigration reform.Speaking with Chris Wallace, Walker tried presenting himself as a principled opponent of all things “amnesty”-related: “I don't believe in amnesty.