California Governor Jerry Brown is on the eve of a self-appointed April 6 deadline to push what he has titled the Road Repair and Accountability Act of 2017, which seeks to impose new gasoline taxes and car registration fees to bring in an estimated $52.4 billion in increased tax revenues over the next decade alone.

Even with the strong support of State Senate President Kevin De León (D-Los Angeles) and Assembly Speaker Anthony Rendon (D-Paramount), Brown is finding it a tall order to rally all of the Democrats in the legislature to support his controversial plan.

In the last election, Democrats picked off enough GOP legislators to gain supermajorities in both legislative chambers. But it will require the votes of essentially every Democrat to pass the taxes in the plan, which under the California Constitutional require a two-thirds vote.

Brown is engaged in a full-court press, now having held press conferences with legislative leaders in the districts of two Democratic state senators who have thus-far refused to support his plan – Senator Steve Glazer (D-Orinda) from the East Bay Area, and Senator Richard Roth (D-Riverside) from San Bernardino County. In the Senate, Democrats have no wiggle room: they hold a two-thirds majority in that chamber by just one vote.

In between these press events, word is that the governor is making a lot of calls, and meeting with a lot of legislators, trying to cobble together the support he needs.

The proposal would increase excise taxes on gasoline by 12 cents per gallon, to a total of 30 cents per gallon (which would be the highest state gas tax in the nation, by far) and create a new annual vehicle fee that would average $51 based on the value of the car or truck. The bill would also index the excise tax rate to inflation, meaning it would increase over time without having to be voted on again by the legislature or the voters.

As of today it appears that the GOP State Senate and State Assembly caucuses are unified in their opposition to the governor’s transportation tax plan. Republicans have long criticized Democrats for refusing to prioritize infrastructure spending out of current tax revenues, rolling out a specific plan to do so. Assembly Republican Whip Vince Fong (R-Bakersfield) also has released a memo from the Legislative Analyst’s Office detailing how current regulations in place to reduce carbon emissions will be leading to significant spikes in gas prices, even if no further tax increases are approved.=

Assembly Republicans rolled out a list of concerns with the plan, with the primary objections being that starting on day one, 30% of the new tax revenues will go to projects other than roads (including parks, workforce apprenticeships, rural bike lanes, boats, trains and local planning grants) and that the plan mandates that less than 5% of funds can go to traffic relief or lane expansion.

Without the support of any Republican legislators, Governor Brown’s job is that much harder because it means that Brown has to win near-unanimous support from Democrats.

Opposition to the Governor’s plan continues to increase, coming not only from conservative groups like the Howard Jarvis Taxpayers Association and the National Federation of Independent Business, but also from the agriculture community, because of the additional costs to bring their products into the marketplace. Environmental groups like the Sierra Club and EarthJustice are also concerned with language placed by Brown into the bill reducing anti-pollution regulations that apply to truckers.

A final challenge for Brown – certainly in terms of pushing through his proposal this week as he would like – is the provision contained in the legislative transparency ballot measure, Proposition 54, passed by voters last November that now requires that bills must be available to the public in their final form for 72 hours before they can be voted on by the legislature.

If Brown starts to open up his proposal to make changes, as he woos reluctant legislators, it would mean pushing a final vote at least into next week.

The new press by Brown, along with De León and Rendon, will be the first major test of the Democrat supermajority, and whether or not – when it matters – they can achieve party unity.

If these tax increases are passed by the legislature, they go into effect without a vote of the people.

Jon Fleischman is the Politics Editor of Breitbart California. You can follow him on Twitter here.