You would never say that Susan Collins is full of surprises.

She signals where she’s going far in advance, so there’s rarely much suspense when it’s time for her to turn.

That’s why last week’s announcement that she will run for re-election for a fifth term surprised – literally – no one. She has been acting like a candidate all year, hitting the fundraisers, running ads on TV, paving the way for a statewide race.

But maybe we should be surprised about something. We may be seeing Susan Collins in the middle of making a big mistake.

Two years ago she turned down a chance to run for governor when she had the approval of two out of three Mainers. She was coming off a re-election campaign in 2014, where she got 68 percent of the vote, including more than a third of people who identified as Democrats.

Now she’s headed into a statewide race where the people who view her unfavorably outnumber those who think she’s doing a good job. 

She has shored up her support from Republican Party’s right wing – they don’t call her RINO anymore – but she has lost the moderate to liberal voters, who associate her with Donald Trump, the most polarizing figure in American politics.

Had she run for governor, Collins could have waltzed into the Blaine House in 2018, getting the job she said she always wanted. But instead, she chose to stay in Washington, champion an unpopular tax bill and provide the deciding vote for a controversial Supreme Court nominee. She not only voted to confirm Brent Kavanaugh before sexual assault allegations against him had been fully investigated, but she delivered a speech in which she said that she believed that his principle accuser, Dr. Christine Blasey Ford, had been assaulted, but she must have been wrong when she said it was Kavanaugh.

Collins has been one of the most sure-footed politicians in Maine history. She just doesn’t make political mistakes,  which is not the same thing as saying that she’s always right. Going back to votes for the Iraq War and the Bush tax cuts, she’s been wrong a lot throughout her career.

But the difference is that all of those votes were popular at the time she made them and they didn’t hurt her when she ran for re-election.  

Whether she was following her inner compass or expertly navigating the currents of popular opinion, she has managed to stay in the safe center for more than two decades. But this time, Collins will have to win a race unlike any she has faced before. Collins will start the campaign “under water” – or with more Mainers giving her an unfavorable rating than a favorable one.

The Morning Consult poll, which tracks the favorability of all 100 senators in their home districts, ranks her the second least popular senator in their home state. According to the poll, 43 percent of Mainers look at her favorably as opposed to 49 percent who see her unfavorably.

Compare that to the summer of 2017, when Collins was considering leaving the Senate to run for governor. She then had a 65 percent favorable rating, with only 26 percent unfavorable, a rating that put her in the top 10 most popular senators.

Her big wins of the past have benefitted from ticket splitters – people who voted for Collins and Democrat John Baldacci in 2002;  for Collins and Democrat Barack Obama in 2008 and for Collins and Democrat Mike Michaud or independent Eliot Cutler in 2014. Each time, she has done better than the other Republicans on the ballot. If the age of ticket splitting is done – and it sure looks like it is – Collins may have trouble finding enough votes.

It’s safe to expect that Trump will turn out his base, fired up and ready to vote for Republicans straight down the ballot. But the president also motivates his opposition, and the people who show up at the polls because they want him out of office don’t look like Collins voters.

In 2016, Trump won the 2nd Congressional District by 11 percentage points but still lost the statewide vote to Hillary Clinton. His combined margin of victory in his best five counties was about half of Clinton’s margin in just one county, Cumberland, which she won by more than 45,000 votes. Collins would need create a lot of distance between herself and Trump to do better than him in more liberal parts of the state and it may be too late for her to pull that off. She can’t shed the image that the only times she votes against Trump’s interests are when her party doesn’t need her.

We won’t know for the next 10 months whether Collins has made a big mistake. But if it turns out she did, we shouldn’t act surprised.

Greg Kesich is editorial page editor of the Portland Press Herald.