By William McKenzie,The Dallas Morning News

President Bush may have spoken to all of America on Monday night about our immigration crisis, but make no mistake: He was nodding toward his party’s right wing. Sending National Guard troops to the border is his way of heading off conservative opposition to the Senate’s broad immigration bill.

Now that he has responded dutifully, will conservatives on Capitol Hill and the radio talk-show circuit line up behind him? Will they back the Senate’s efforts to pass comprehensive immigration reform before Memorial Day?

I hope so, because the Senate plan is good public policy. Along with placing even more agents and technology along the Mexican border, it would allow in more foreign workers and offer some of them a long path to citizenship. Bush rightly emphasized that latter point Monday night in his speech.

But forget the policy part, for a moment. There’s a huge political dimension in play. Nothing less than a turnaround of Bush’s presidency is at stake.

I know I’ve written that several times this year. And many e-mail critics would tell me that Bush already has lost his presidency and that I should give it a rest.

Thanks, but not just yet.

Going back to his early days on the Texas campaign trail, I’ve always found Bush a shrewder politician than meets the eye. I also like his philosophy of “government if necessary, but not necessarily government.” And when it comes to immigration, he stands to return to the Bush of old, the one who promised bipartisan solutions.

I’m not blind. Bush clearly is about to lose it all. He’s at 31 percent in some polls; Republican conservatives are angry; stories abound about his waning influence in his last 1,000 days in office.

Iraq won’t get him out of the Dumpster, either. We may not know for 20 years whether that move turned around the Middle East or was a fool’s errand.

So either fate serves him another issue – as it did Ronald Reagan when two Russian presidents died and Mikhail Gorbachev emerged – or Bush gains momentum on the domestic front.

That’s why the next two weeks are so significant. Bush can’t control fate, but he can try to regain his domestic juice, starting with a victory on immigration.

If he can capitalize on Monday’s speech and get the Senate to pass a major overhaul of our immigration laws before month’s end, he lives to fight another day for policies that arguably are as important as any since the 1960s civil rights legislation. And he gains more time to persuade skeptics in the House to allow immigrants to become legal workers.

Some want to erect a wall between the United States and Mexico and deport every illegal immigrant. Bush clearly was speaking to them last night with his National Guard move.

What he needs to do next, as one Republican close to the White House told me, is show recalcitrant conservatives why allowing more foreigners to work here makes for a better tent for America – and for the GOP.

Without a “guest worker program” that lets border agents know who’s legal and who’s not, we’ll keep throwing every last available cent at securing the border. And that will be as effective as Prohibition was at stopping the sale of alcohol, as Tamar Jacoby of the conservative Manhattan Institute sums it up.

If the Senate fails to pass a serious immigration bill, the issue dies. And so, perhaps, does Bush’s presidency. He won’t have many other chances to get Big Mo going on the domestic track.

The fall elections are soon upon us, and then Bush is in the last two years of his presidency. And the number of days and issues he has to redeem itself will only dwindle.

“This president can now measure in a relatively few number of months his window for effective governance,” GOP strategist Ed Rogers recently told The Washington Post.

The White House evidently recognizes the stakes are high. Otherwise, Bush wouldn’t have gone live Monday night. It’s time for him to keep rolling the dice because his presidency rests on gaining momentum over the next two weeks.

William McKenzie is an editorial columnist for The Dallas Morning News. Readers may write to him at the Dallas Morning News, Communications Center, Dallas, Texas 75265; e-mail: wmckenziedallasnews.com