Susan Collins is underwater. If you said Monday follows Thursday, it would be easier to believe.

But, in the Morning Consult quarterly tracking poll, more Mainers viewed their senior senator unfavorably than favorably, by a rate of 48 to 45.

That’s a 16 percent fall from where she was at the beginning of the year in the same poll, and a far cry from where she has stood for years, when she was ranked among the most popular senators in the nation.

Now her picture lands in the gallery of the 10 least popular, with only Senate Majority Leader Mitch McConnell, a man who makes Machiavelli look like a rube, beneath her.

What does it mean? First some caveats.

It doesn’t mean that she is going to lose the next election.

Despite his unpopularity, McConnell is the odds-on favorite in his race, and of the other eight senators in the Morning Consult’s least popular gallery, four  were on the ballot last year and won.

Former Gov. Paul LePage never won any popularity contests, and he won two statewide races. Donald Trump is nothing but formidable, even with a job approval rating that rarely nudges 40 percent.

The election is more than a year away and the Democrats won’t know their nominee until next June. A lot can happen in that time.

But, still – underwater? And what has to be frustrating is that her poll numbers may have changed, but she hasn’t.

Collins, along with other Republicans like Olympia Snowe and William Cohen, had been able to forge a political identity outside the party label.

Voters saw them as “their” senators, ones who would represent them against the interests of both parties in Washington. Collins is where she is today because Maine voters split their tickets.

In 2008, Barack Obama trounced Republican John McCain in Maine’s presidential race, 57 percent to 40 percent, while Collins took 63 percent of the vote. According to 2014 exit polls, Collins got the votes of 39 percent of self-identified Democrats and 37 percent of liberals in her landslide victory over Shenna Bellows..

But the world has changed since the last time Collins faced the voters, and the change is named Donald Trump.

Trump owns the Republican Party now, and there is no room for a Republican identity outside his shadow.

The never-Trump movement fizzled, and its members have either changed their registration, like columnist George Will, or fallen in line, like Utah Sen. Mitt Romney. The only Republicans who openly criticize the president are the ones who have retired from public life, like former House Speaker Paul Ryan.

Collins’ attempt to create her usual political space has not worked. She remains the most bipartisan senator of either party, but according to CNN, Trump’s first year in office was her most partisan, voting along party lines more often than at any time in her career. That both things can be true tells you more about America than Collins.

The vote that is cited most often cited as the reason for the change in the public’s view of Collins – her vote to confirm Supreme Court Justice Brett Kavanaugh – is exactly like the votes that made her popular. Collins has never voted against a Supreme Court nominee, no matter which party was in power, but this time it was different.

Kavanaugh was nominated by Trump, who promised to name only anti-abortion justices to the court. His name came off a list of judges pre-approved by the right-wing Federalist Society, and under McConnell’s leadership (with Collins’ vote) the Republicans eliminated the filibuster for Supreme Court nominees, making it possible to ram through far-right judges on a partisan basis.

The process reeked, and when Dr. Christine Blasey Ford came forward with credible allegations of long-ago sexual assault, the Kavanaugh nomination became a symbol of everything wrong with where Trump was taking the country. Others said that pushing ahead would damage public confidence in the institution, but Collins pushed ahead. And now she’s seeing the result

It will be interesting to see how she navigates this new environment.

She is probably more popular with rank-and-file Republicans now than at any point in her career, but the Maine Republican Party is not the one that nominated her in 1996. It’s now run by LePage loyalists, and it’s hard to imagine Collins embracing it’s anti-immigrant, anti-abortion and anti-vaccine agenda.

In the past she has been able to run independently from the party, but these days, ticket splitting is out of style.

Collins has never had to win a close, partisan race in a state that’s deeply divided about the direction of the country. But that’s the kind of race you need to run when you are underwater.