House Speaker Robert DeLeo will have the House vote a $600 million tax plan next week, with proceeds set to go to improvements for the MBTA, regional transit agencies and other transportation projects. It's the first step in an inevitable House vs. Senate clash over how to approach transportation funding. Here are four key issues to keep an eye on as moderates and progressives try to influence the bill over the coming days.

It's not a plan for spending more on the MBTA

The House's tax bill would raise up to an estimated $612 million dollars in new revenue through higher fees on ride-hailing and rental car companies, and increases to the gas and corporate taxes. As it stands, DeLeo's plan only dedicates $54 million annually to the T and regional transit authorities. The gulf between the money that would come in under the tax bill, and the amount of spending stipulated for the T lead Gov. Charlie Baker to claim that his own budget plan would give more to the T without having to raise taxes. That could change later this spring when House leaders reveal their own budget bill, which could utilize the new tax revenues to dedicate a much larger share of the pie to the MBTA.

Election year pressure

As loyal to DeLeo as most House Democrats are, it's not going to be easy to get a super-majority of members to vote for a $.05 increase in the per gallon tax on gasoline, or the accompanying $.09 cent hike to the tax on diesel fuel, in an election year.

Majority Leader Ron Mariano (D-Quincy) laid out House leadership's strategy for getting members on board.

"This is a tax increase in an election year and everyone is looking to have an impact on their district," Mariano told reporters when the bill was released last week. Mariano said the approach for building consensus around the bill was to listen to what members wanted for their districts, whether inside the MBTA zone or in areas with few public transit options.

With the $600 million in place, the House will have leeway to add spending to a long-term transportation borrowing bill and the annual budget to appease members and give them something to campaign on back home.

"This is just the beginning. This is no way near the identified needs that the Speaker alluded to in his remarks. We understand that," Mariao said.

The Senate will get in on the action

About two hours after House leaders officially released their tax bill, Pittsfield Sen. Adam Hinds alerted the State House press that the Senate's own efforts to review and raise taxes was set to meet this Thursday. Hinds' working group expects to present it's own tax bill to rival the House's. Shortly after Hinds' missive, Senate President Karen Spilka offered that "the Senate looks forward to beginning in earnest the exchange of ideas between the House and Senate that will result – we hope – in a safer and more effective transportation system for the entire Commonwealth."

Progressives will get their chance to push the bill left

All House members, including the House Progressive Caucus, have the opportunity to file amendments to the House tax bill before it's debated next week. If any progressives are disappointed that the Speaker's bill doesn't raise enough new revenue or relies too heavily on the gas tax, they can push for their colleagues to make changes.

Progressive Caucus members had signalled they'd prefer increasing the tax on corporate earnings over the gas tax paid by all drivers regardless of their means. DeLeo's bill increases both taxes, and charges the state's highest-earning companies more.

"We are looking at the details of it, but I can say we are pleased that the corporate minimum tax, and that it's tiered, is in there. We were looking primarily that there would be shared responsibility, and that comes through in this bill," Progressive Caucus co-chair Rep. Tricia Farley-Bouvier told the State House News Service.