Maryland Comptroller Peter V. Franchot (D), right, and state Senate President Thomas V. Mike Miller (D). (Robert A. Reeder)

Instead of sharing some eggnog or perhaps a round of caroling on the streets of Annapolis, Maryland Comptroller Peter Franchot and Senate President Thomas V. Mike Miller Jr. are celebrating the season with a highly public exchange of letters that make clear their mutual contempt.

On the surface, the spat between the two Democrats involves portable air-conditioning units for Baltimore County schools. But the deeper clash is about Franchot’s view of his role as an aggressive guardian of the public interest and Miller’s assessment that the comptroller is a headline-hunting opportunist who sticks his beak into local affairs for political gain.

Franchot, who often allies himself with Republican Gov. Larry Hogan, has pushed for months to change rules barring the use of state construction funds for portable units to cool sweltering classrooms in buildings without central air. He wrote to Miller (D-Calvert) and House Speaker Michael E. Busch (D-Anne Arundel) on Dec. 11 to express his displeasure that the state Senate’s representative on the Interagency Committee on School Construction had moved to delay action so that lawmakers could have more time to consider the issue.

Franchot said he would be happy “to facilitate a discussion between the leadership of your respective chambers, and the children, families, employees and teachers who continue to suffer under conditions that none of us would ever tolerate within our own places of employment.”

Busch’s response, if there was one, has remained private. But Miller wrote a letter this week that quickly found its way into reporters’ inboxes, saying he was “puzzled” by Franchot’s “overly dramatic and unnecessary adversarial tone.”

He mentioned a Dec. 8 Washington Post story about millions of dollars in Montgomery County income tax revenue that Franchot’s office mistakenly sent to other county municipalities, and he wrote that the General Assembly should hold a hearing about problems in the comptroller’s office.

“You seem increasingly content to pursue your personal and political interests and seem to delight in basking in the glow of press releases while ignoring your constitutionally mandated duties,” Miller wrote.

On Thursday, Franchot delivered his own season’s greetings. He defended his office, which he said has earned both statewide and national recognition for service to taxpayers, reflecting “our time-honored commitment to what I call ‘The Three Rs: Respect, Responsiveness and Results.’ ”

The three-term comptroller also noted that he had been reelected in 2014 with 63 percent of the vote in what proved to be a bad year for Maryland Democrats — “particularly for state and local candidates in Calvert County [part of Miller’s senatorial district] where your political tutelage catapulted our party’s gubernatorial nominee to 30 percent of the general election vote.”

Franchot suggested that Miller — an 11-term incumbent and the longest-serving state Senate president in the country — was angry not about the air conditioners, but about Franchot’s closeness with the state’s Republican governor.

“Based on some of your more recent private comments to me — the contents of which I shall not repeat for fear they shall be reposted in family media outlets — my sense is that your sudden and newfound concerns over the performance of my office are actually based on my well-documented willingness to reach across partisan lines,” he wrote.

Franchot warned that ignoring conditions in Baltimore County schools would place Democrats on the wrong side of an important issue at a time when they should be marshaling support. “Put more directly, senator, it would be a staggering display of political incompetence that neither your caucus members nor the Democratic Party as a whole can afford right now.”

Franchot ended on a jolly note.

“I look forward to hearing from you and, in case we don’t speak in the days to come, I’d like to wish you and your beautiful family a Merry Christmas.”