Are Republicans only against immigration Reform because the voters they thought they would have turned away?

Reagan passed an across the board Amnesty to get a huge voter base for Republicans, Bush supported reform as well to try and increase that base, he signed a bill making it easier to hire immigrant workers right before he left office. But with all the rhetoric on immigration and bashing towards Hispanics, they have lost the Latino vote. Is losing the Latino vote the only reason why they now oppose Immigration reform?