Bush has had six years to establish better controls over the border and to enforce existing laws regarding the hiring of illegal aliens. For four of those six years, both houses of Congress were controlled by the Republicans. The Administration's record was abysmal, worse than that of the Clinton Administration, which was poor.
Bush isn't good on immigration, although he is doing exactly what he said he would do during his campaign.
But he doesn't support amnesty, or at least he would prefer a program that is NOT amnesty -- I fear he will go along with amnesty if that's what the democrats send up.