AUGUSTA, Maine — Gov. Paul LePage is drawing a line in the sand on killing Maine’s income tax.

In a letter sent to legislative leaders from both parties on Monday, LePage revealed that he’s filed preliminary paperwork on a bill to eliminate the tax by 2020. He’s given leadership until 5 p.m. to sign on as cosponsors to the bill.

Left unsaid is the implicit threat that goes along with not joining the governor. Earlier this year, he said he’d campaign against any lawmaker — Democrats and Republicans alike — who didn’t back him in his quest to end the income tax.

The proposal would amend Maine’s constitution to bar the state from collecting income tax after Jan. 1, 2020, but says nothing about how to get from collecting more than $1 billion in income tax annually to collecting none in just five years.

Lawmakers are currently chewing the massive tax reform plan contained in LePage’s two-year budget for fiscal years 2016 and 2017, which contains a reduction in the income tax worth more than half a billion dollars as its centerpiece.

But a reduction has never been LePage’s end game. Since winning re-election in November, his rhetoric has focused on eliminating the tax altogether. “My vision for Maine is a Maine without an income tax,” LePage said during his State of the State address in February.

In town hall meetings around the state, the governor has touted the constitutional amendment as the surest way to seal the income tax’s fate regardless of future election results. He reiterated that argument in the letter.

“To ensure that any income tax cut is permanent and cannot be reinstated by future legislatures, it is critical that we change the Constitution,” LePage wrote. “We must remove the burden that the personal income tax places on Maine families — from retirees on fixed incomes to job creators — by amending the Constitution of the State of Maine to eliminate the personal income tax levied by our State once and for all.”

Given the power dynamic in the Legislature, a constitutional amendment to repeal the income tax is far from a sure thing, even if LePage can convince every Republican to get on board.

Constitutional amendments require two-thirds support of the Legislature before they can even go to voters for approval, and Democrats’ majority in the House will make reaching that threshold a tough task for the governor.

If he is successful, though, 2016 would shape up to be one of the most consequential elections in quite some time. Adding the income-tax killing amendment on the ballot in 2016 would most likely drive conservatives to the polls in droves, boosting the GOP’s prospects in a presidential election year — a time in the election cycle that usually favors Democrats.

And if the presence of a presidential election and potential income tax-killing referendum wouldn’t ratchet up the turnout stakes enough, it’s also the year that proponents of ranked-choice voting will put their referendum out to voters, and is likely to be the year Mainers vote on whether to legalize recreational marijuana.

Watch for updates.

Follow Mario Moretto on Twitter at @riocarmine.

Mario Moretto

Mario Moretto has been a Maine journalist, in print and online publications, since 2009. He joined the Bangor Daily News in 2012, first as a general assignment reporter in his native Hancock County and,...