There's growing support on Beacon Hill for taxing million-dollar earners at a higher rate than the rest of us, but that's no guarantee lawmakers will act quickly to put the proposal before voters.

Before the so-called "Fair Share" amendment can go on the ballot in 2018, it needs to pass through two sessions of the Legislature, one this year and another in the 2017-2018 session.

It would add a 4 percent surtax to incomes over $1 million annually and, supporters say, would raise over $1 billion a year to be dedicated to education and transportation in the state. The state constitution does not allow different income tax rates, so the tax would only happen by amending the document, a lengthy process involving signature gathering, legislative approval and a ballot referendum.

Organizers behind the proposal say they're prepared for the Legislature to debate the tax hike tomorrow and are confident they have more than the 50 votes they'll need to advance the proposal. However, leaders with Raise Up Massachusetts, the coalition that's backing the amendment, don't expect Wednesday's convention to include a vote on it. More likely, the Convention will recess until this Spring or Summer when they can focus on the tax hike.

The income tax proposal is the last of ten amendments on the convention calendar. Senate President Stan Rosenberg indicated Monday that he would take the amendments in order and only take up the tax proposal if lawmakers can work through debate on the nine others.

"We may or may not get that far in the calendar, because I think it's item number 10, but I'm hoping we'll have some debate at the convention on Wednesday," Rosenberg told reporters Monday after meeting with House Speaker Robert DeLeo and Gov. Charlie Baker.

"It's really very difficult to say how far you're going to get at this point because you really don't know until you get there, in terms of where people's interests or concerns lie," DeLeo agreed.

The biggest factor the tax hike's proponents have in their corner is the support is Rosenberg, who chairs constitutional conventions. Even if the Convention does not get to it, Rosenberg has incentive to clear the proceeding amendments out of the way to clear a path for the tax increase to be the focus of another convention between now and the end of July, when lawmakers will recess for the year.

Beacon Hill hasn't seen a Constitutional Convention this exciting since the 2004 debate over an amendment that would have prohibited gay marriage.

In fact, the constitution hasn't been amended since 2000, when felons were barred from voting in elections.

Most constitutional conventions do not take up any legislation before moving to recess and usually last for less than a minute.