President Bush is caught in a terrible “spiral of silence.”

After his job approval numbers slipped under 40 percent last month, most Republicans in Congress lost their voices. They seemed incapable of rising to their president’s defense. If they’ve praised any president in the past month, it’s been dearly departed Ronald Reagan rather than George W. Bush.

As a pollster, someone who’s supposed to live and die by the numbers, it’s ostensibly hard to fault the speechless Republicans. It’s almost a surprise that more GOP members aren’t overtly distancing themselves selectively from one or two of the president’s more unpopular policy initiatives. But a closer look at some poll numbers suggests that the silent treatment is a mistake.

Looking at four nationwide public polls taken in the past month that asked both a presidential approval-rating question and a generic congressional-ballot question, it appears that Bush and Congress are linked closer than members acknowledge. In each poll, Bush’s approval rating is within the margin of error compared with support for GOP congressional candidates.

The CBS poll, conducted April 6-9, actually shows Republicans in Congress are upside down, with generic-ballot support of just 34 percent for the GOP, three percentage points below Bush’s job approval rating of 37 percent.

Republicans who believe that ignoring Bush will sever the link between their political fortunes are kidding themselves. Building up Bush’s job approval is essential to Republicans’ doing well in the November elections.

Sure, most entrenched Republicans can survive low presidential approval ratings. But enough Republicans will be endangered by a president with sub-40-percent approval ratings that the GOP needs to rally behind Bush to ensure its majority status.

The Republican caucuses should get in touch with James Carville’s speakers bureau and book the former Clinton apologist to deliver a speech-length address on loyalty, something that the bald one covered expertly in his 2000 book, Stickin’: The Case for Loyalty. You don’t have to admire or even approve of Carville’s disgusting defense of Bill Clinton’s hypersexuality, but Republicans could learn a thing or two from the Democrat consultant’s Tammy Wynette-like pleas to “Stand by your Man.” I can imagine that if Democrats had treated Clinton like Republicans are treating Bush, Carville would have called them out. Heck, he might even call out Republicans for abandoning their own man.

The most troubling aspect of this matter is that Republicans aren’t rallying behind such a principled leader. President Bush has been a paragon of principle over politics. By comparison, Clinton was a cad who deserved no one’s support based on principle. Carville’s support was pure politics. Why can’t Bush find a similar defender?

Unfortunately, no one seems ideally suited to the role. Karl Rove might fit were he not on the White House staff, a job that deprives him of the time and opportunity to be the president’s chief everyday defender.

Sen. John McCain (R-Ariz.) has been Bush’s able guardian in several instances during the past year. He could do the job. But as a candidate for president, he cannot be expected to do much more than he’s already doing.

One enticing possibility for the job would be Bush’s brother, Gov. Jeb Bush of Florida. Jeb has extraordinary media savvy, understands the challenges facing the president and his party and would be an intriguing protagonist.

Someone needs to step forward. It could be a career-maker move — and save a party’s majority in Congress to boot.

Hill is director of Hill Research Consultants, a Texas-based firm that has polled for GOP candidates and causes since 1988.