Here’s a fun bar bet: What town in Maine has the most Republicans?

Caribou? Bangor? Auburn?

No. It’s Portland.

A Republican might not be able to win a local election in Maine’s biggest city, but since it is the biggest, it has more of everything, including Republican votes.

Paul LePage resented Portland so much that he allegedly ordered his marine resources commissioner to build a new port somewhere else. But on Election Day in 2014, the 6,724 votes he got in the city were the most he got from in any municipality in Maine.

Of course, there were three times as many votes for the other guy, but since there’s no statewide version of the Electoral College, a vote in Portland is just as good as a vote in Rumford in a statewide race.

As we head into the last week of the 2020 campaign, candidates are scrambling to get every vote they can. And the high-stakes battle for partisan control of the United States Senate could come down to how well Republican Susan Collins will do in Portland and its surrounding towns.

Collins is facing the toughest challenge of her career in a four-way race. The public polling shows her behind Democratic House Speaker Sara Gideon, but nothing about the way the candidates are talking or the money that they are spending indicates that either side think this is anything but a close race.

Looking for any advantage she can get, Collins has taken to pointing out that Gideon grew up in Rhode Island and that she has lived in Maine for only 15 years. When Collins points out that Gideon lives in Freeport, she draws out the first syllable with such disdain that it’s clear the Caribou native questions whether that should even count.

The “People from Away” trope may play well in some parts, but it’s probably not going to work in Greater Portland, where a lot of people come from other places and still get to vote. Like her glowing endorsement from the Christian Civic League of Maine, staunch opponents of abortion and LGBT rights, it appeals to voters Collins should already have socked away.

No one expects Collins to do as well in southern Maine as she did six years ago, when she won Cumberland County by 33,459 votes, picking up 13,273 votes in a close loss in liberal Portland. But the question is whether she will be able to keep it close enough to pull off a statewide win.

One of the oldest political truths in Maine is that candidates based in the 2nd Congressional District have an advantage when they are running statewide. The theory is that even though the two districts are supposed to have roughly the same populations, the 2nd District is harder to campaign in because it covers so much territory.

Bill Cohen, Olympia Snowe, John Baldacci and Collins are all winners with a 2nd District base. Two notable exceptions, George Mitchell and Paul LePage, started in Waterville, which is currently in the 1st District, but close to the line.

The last few election cycles have challenged that wisdom, though.

Everybody remembers that Donald Trump won the 2nd District by 10 percentage points in 2016, causing Maine to split its Electoral College votes for the first time in history.

But we sometimes forget that Hillary Clinton won statewide anyway, and it wasn’t even that close.

In the 2018 gubernatorial race, Janet Mills built up a 40,000-vote cushion in Cumberland County that offset losses in most of the 2nd District counties on her way to a comfortable win over Republican Shawn Moody.

Collins’ bid for a fifth term could come down to the Greater Portland towns outside the city, where she has always done well but which have been trending toward Democrats.

The key battleground community might be Scarborough, which Collins won by more than 4,000 votes in 2014. But the town went for Clinton in 2016 by a nearly 2,000-vote margin, and for Mills in the governor’s race two years later by 1,200 votes.

Will Scarborough voters remember their affection for Collins and vote for her, even if they  again reject Trump on the same ballot?

Or will they turn to Gideon, a fellow Greater Portland suburbanite, accepting her view that voting for Collins would give Republicans the power to obstruct another potential Democratic president?

This is a tight race that will probably be settled through ranked-choice voting tabulations that take a few days to set up.

But a lopsided margin in a town like Scarborough will tell us a lot on election night.