Amidst the hatreds, the envy, the gossip, the vituperation, the self-pity, and the curdling contempt for fellow officers, one single light that shines through Phil Kearny's letters to his wife is William Franklin: his capacity; his potential; his intelligence; his raw talent. I have long used Kearny as my window into the Franklin phenomenon during the ACW.
Grant, in 1864, made an issue of restoring Franklin to command because, I believe, Franklin had the gift of impressing people, new acquaintances as well as those who knew him for years. He eventually disappointed Kearny as he would McClellan, Banks, and Grant. All seemed to agree though, that Franklin was special, and in a strange ageing of his West Point social scene, Franklin remained "at the top of his class" long after graduation through most of his prewar career.
On some level, Franklin impressed Chase. McDowell would be the senior partner of this Treasury Department duo, but Franklin was not unwilling or unloved. McDowell and Franklin were not a shotgun marriage - they had chemistry and accomplished major military tasks together under Chase.
My hunch is that Franklin affected McClellan's decision to retain McDowell after Bull Run. We also have McClellan preserving McDowell-Franklin as a team in spring of 1862 (corps commander/division commander) and McClellan giving McDowell the largest corps and the most decisive mission in the 1862 Richmond campaign. Again, my hunch is that this is partly Franklin's doing. When the I Corps was withheld from his command and McClellan suspected McDowell of intriguing for an independent role, we have documentation showing Franklin intervening with McClellan to defend McDowell.
When Lincoln forced McDowell onto the unwilling Scott as deputy and department commander, hiatus arrived for the McDowell-Franklin skunkworks, which was then planning an advance on Centreville. The plan went public, and legit, with both men assuming proper military roles within a defined, legal military hierarchy. Lincoln thus made honest men of them and Chase lost his military advisors.
The best known McDowell-Franklin incident comes later and is of little moment to their partnership but of major significance to McClellan. I speak of that famous Cabinet meeting in January '62, the bottom falling out of the tub, etc. To the garden variety ACW historian, McDowell and Franklin have been summoned to a cabinet meeting to help decide what to do during McClellan's sickness. This kind of historian sees no special point in such a choice of advisors. It's as if two random officers were chosen by lot to give an opinion and go home. But no one steeped in the early war can miss the overpowering significance of this pair in these circumstances and this setting advising the president and cabinet following an invitation from Chase.
You have to be obtuse to miss the point, but obtuse is something ACW historians do especially well.
McClellan was not so himself. McDowell-Franklin, lately just a couple of blocks in a military org chart, were suddenly on the point of revival as an ad hoc, defacto military high command reprised to offset the shortcomings of yet another general-in-chief. This time it wouldn't be Scott they routinely bypassed. GBM evacuated his sick tent to attend the meeting.
Historians have a hard time understanding McClellan's behavior at that meeting. Again, the deep reader of early war history sees easily what McClellan is doing. He is re-establishing himself with Chase as the principal Ohioan military asset in Chase's orbit; he is publicly displaying confidence in the wisdom and judgement of his political patron (Chase) by vouchsafing unique information not available to Lincoln and the chain of command; he is displaying loyalty and fealty to the man aiming the two gun barrels of McDowell and Franklin at his position and future. He is giving Chase - publicly - leverage over Lincoln and the rest of the cabinet. What baffles historians is actually a bravura performance that sends the dual menace back to the dusty blocks of a static organization chart.
Given the threat that McDowell-Franklin posed to GBM, it is another tribute to Franklin's occult charm that as 1862 developed, McClellan turned on McDowell but not Franklin.
The reprise of McDowell-Franklin in 1862 casts light on their earlier role and is worth a brief look.