So sure was Robert DeLeo of House Speaker-to-be Ron Mariano's loyalty that the steely-eyed DeLeo didn't blink when Quincy Democrat Mariano began several years ago to quietly solicit support to succeed the once-called "Speaker For Life."

Now the transition is almost complete, with even the co-chairs of the House Progressive Caucus pledged to the 74-year old Mariano.

Mariano's ascension takes a chapter from the rules according to DeLeo, the foundation of which is to make sure there is a rock-solid majority in favor of any proposal before scheduling a vote. On rare occasions — the recent vote on police accountability is an example — the situation may get close. Still, the result is predictable: The speaker never loses.

There is no evidence to suggest Mariano will rewrite that playbook. That means that the House — rather than the state Senate — is likely to remain the arbiter of what does and doesn't become Massachusetts law.

To most members, Mariano, soon the 86th speaker, promises stability. And in a state that is wracked with coronavirus, a steady hand is a prized commodity.

Former Majority Leader Mariano has replicated the broad support from all stripes of Democrats that kept DeLeo in power for nearly 12 years.

"In any institution, you look for experience, and I think he's the most experienced candidate," Easton Rep. Claire Cronin, a supporter of Mariano and chairwoman of the House Judiciary Committee, told GBH News when Mariano announced his intention to seek the speakership.

DeLeo vacated the Winthrop seat he's held for nearly 30 years for a job at his alma mater, Northeastern University.

DeLeo leaves the House just one week before the end of the legislative session, with lawmakers potentially set to take last-minute votes on issues as far ranging as online sports betting, housing production, transportation funding, climate change preparations and more.

There will be no honeymoon for Mariano, as work must begin in January on next year's budget plan, which will be difficult to balance because of deteriorating tax revenues and inconsistent aid from the federal government.

"I tend to believe that when you're in a hurricane, you want the old oak tree and not the young one you just planted," Cronin said. "We're going into really stormy, stormy times ahead."

In a public statement sent the day DeLeo announced his interest in Northeastern, Mariano wrote that members of the House are eager to recover from the pandemic and revive the economy, curb the cost of health care, build housing and transportation infrastructure and address climate change.

"I believe I have earned the trust and confidence of my colleagues and that I have gained their support to lead the House forward," Mariano wrote.

There are grumbles that Mariano will not be as open to progressive legislation as his predecessor. Progressives from outside the State House are weary that Mariano won't try hard enough to push through the select number of socially progressive bills, such as transgender legislation, that DeLeo was known for.

"It’s extremely telling of the state of the Democratic Party in Massachusetts that the Democrat electeds can’t organize themselves to find a leader who is at least as left-leaning as DeLeo, who set a pretty low bar," said Rebecca Pinn, a Democratic State Committee member and secretary of the Young Democrats of America.

Speaking to GBH News the day before his elevation, Mariano said he may be more willing to push legislation to the floor than DeLeo had been.

"You try to build a consensus, but at some point you have to put it to the body and let them decide. I think that would be one of the changes you may see or may recognize as being a little bit different."

Inside the State House, Mariano is seen as a moderate Democrat closely allied with DeLeo. As majority leader, Mariano's voting record was essentially identical to DeLeo's and fully in step with the mainstream of the House.

Planned Parenthood of Massachusetts considers Mariano an "ally" on its annual scorecard of lawmakers. Other left-wing groups, like Progressive Massachusetts, take a dimmer view. The group gave Mariano a "D" ranking for support of their very progressive agenda.

The right wing isn't overly fond of Mariano, either. The anti-tax Massachusetts Fiscal Alliance rates him at 2%, a bit lower than the average Democrat and identical to DeLeo's score.

Rep. Russell Holmes of Mattapan was the only House member planning to challenge Mariano. But he thought the better of it.

Two retiring representatives, Denise Provost of Somerville and Jonathan Hecht of Watertown, were the only other members speaking out against Mariano's elevation. The pair urged fellow House progressives to withhold support from Mariano, who they wrote in CommonWealth is well to the political right of DeLeo.

If House progressives "acquiesce quietly in Mariano’s election, they will be complicit not just in flouting basic democratic norms but also in elevating to the powerful speakership someone whose record shows indifference, if not outright hostility, to progressive values and legislative priorities,"Provost and Hecht wrote.

Former Ways and Means Chairman Jeffrey Sanchez served with Mariano for years and worked closely with him on health care policy. Sanchez called Mariano "a conductor in the well" of the House chamber who masterfully negotiates deals on the floor and in the back rooms of the State House.

"The average person doesn't see him, but he has shepherded and ushered in major pieces of legislation that have affected every life in the commonwealth," Sanchez told GBH News.

Another supporter, Rep. Josh Cutler of Duxbury, said Mariano has been a teacher and mentor in the House by cutting to the core of issues and dealing honestly with members. Mariano has a reputation for plain speaking, which most interviewed seem to appreciate.

"Anytime there's a tough vote or a thorny issue or something I need some guidance on, he's someone that I really look to, and I think a lot of other members look to. He's someone who has a lot of wisdom about these things," Cutler said.

Even before the speakership vote, there was speculation that the septuagenarian Mariano's term may not last more than a few years, generating speculation of who would become the new "speaker-in-waiting." Ways and Means Chairman Aaron Michlewitz of the North End, 42, is among the mentioned, as is Easton's Rep. Claire Cronin, who could hold a senior leadership position under Mariano.

Pensions often figure in conversations on how long a political leader in Massachusetts will choose to remain in office. DeLeo is leaving with an annual pension estimated to be around $135,000. Mariano would need to serve as speaker, and earn the higher salary that comes with it, for three years to maximize his own annual retirement payout. That would mean reelection as speaker in 2023 and serving until at least the end of that year.