I was reading a book called "Clashes: Air Combat over Vietnam 1965-1972" by Marshall L. Michel III. I was largely looking for a passage which described the use of F-4's in 1967 performing CAP's over the airfields to either catch MiG's taking off (they couldn't bomb the fields, but they could shoot the planes once airborne) -- and that was on page 88.
Regardless, I found another passage that's of interest here on page 90
....In March the northeast monsoon kept the weather bad and limited the
number of strikes, but the strikes escalated when, on March 10, the Thai
Nyugen steel works were bombed for the first time. In Washington
another battle continued: Rolling Thunder was becoming ever more con-
troversial and had resulted in a sharp division between the military and
the secretary of defense, with the President in the middle. The military
continued to press for an increase in the bombings and the relaxation of
other restrictions, including the mining of Haiphong harbor; Secretary of
Defense McNamara believed the bombing was achieving its objectives
and still feared a confrontation with China or the Soviet Union.
The emboldened stuff is emphasized by me.