Former Gov. Paul LePage (left) and Gov. Janet Mills. Credit: File / BDN

Maine Democratic Gov. Janet Mills and former Republican Gov. Paul LePage have a clear path to their gubernatorial showdown.

The deadline for party candidates to file paperwork to run for governor passed Tuesday with no challengers for Mills or LePage. The deadline for independents to file isn’t until June 1.

For now, it’s shaping up to be the first two-candidate gubernatorial in decades in a state that prides itself on independence — and in which independent candidates have had some success.

With no primary challengers, Mills and LePage can focus on battling each other instead of challenges from within their own ranks.

It’s going to be a costly — and potentially bruising race.

The Maine Republican Party announced that it has booked $3.9 million in campaign ads for this cycle, and national groups will likely be involved as well, the Portland Press Herald reported.

Mills had raised $1.6 million and LePage $900,000 through year’s end, according to state reports.