Rising pressure from G.O.P. led Sen. Craig to resign. Many Republicans felt they had lost their political margin for error.

From The New York Times:

Although Mr. Craig had pleaded guilty only to disorderly conduct in an airport restroom, . . . it involved allegations of homosexuality and put Mr. Craig’s party in an awkward position, given the rhetoric that Republican strategists often employ on an issue that agitates their party’s base voters.

With the corruption issue having weighed down some of their Congressional candidates in the disastrous 2006 elections, Senate Republicans saw Mr. Craig as inviting even heavier damage, especially on the heels of ethics cases involving two other Republican senators, David Vitter of Louisiana, who was the client of a dubious escort service, and Ted Stevens of Alaska, who faces a widening inquiry into whether he traded official favors.

One Republican senator did privately voice reservations about the rush to force Mr. Craig out, compared to the lack of any public reprimand of Mr. Vitter. This senator and others said the different approach made it appear the party was simply less tolerant of homosexual conduct.

But that was almost certainly a minority view.

President Bush’s weakened political status on Iraq, combined with the reality that 22 Republicans face re-election in 2008 (compared with only 12 Democrats) made the Republican caucus extremely reluctant to weather a protracted ethics investigation into Mr. Craig’s misconduct, which some senators viewed as far more shocking and distasteful than any of the other problems staining their party.

If the Republicans seemed draconian, it was because many of them felt they had lost their political margin for error.