Maine’s March 3 presidential primary will consume all the available political air for the next three weeks. After that, the U.S. Senate race featuring Susan Collins’s attempt to win an unprecedented fifth term will take center stage through the June 9 primary election.

It will be an interesting show. The candidates, through Dec. 31, have raised nearly $19 million and spent $10 million. Before the U.S. Supreme Court’s misbegotten Citizens United decision in 2010, these would have been staggering sums, but are now routine even in small states like Maine.

Nor does this include the vast clouds of “dark money” rolling in from all quarters — “independent” spending not controlled by any candidate. There’s so much money sloshing around it may not matter in the end; human beings can absorb only so many political ads before ignoring them.

The reason for all the early money is clear: For the first time, Collins is vulnerable to defeat. Her political problems have multiplied since her rare bold move in 2016, saying she wouldn’t vote for Donald Trump, calling him unfit.

Trump has driven the last vestiges of moderation out of the Republican Party, and Collins has presented herself as moderate throughout her career. Impeachment thus presented the classic no-win situation.

Collins voted, as expected, to acquit Trump, saying she thought he’d learned a lesson, a statement he blew up just hours later. Collins then said she should have said she “hoped” he’d learn — not that it really matters.

While preventing a GOP eruption, Collins courted a quieter decline among Democrats and independents who’ve stuck with her over the years. She didn’t help her cause, describing Trump’s attempted shakedown of the Ukrainian president as a “difficult-to-define, noncriminal act.”

So Collins, like Trump, faces a referendum on the Republican brand of government. Attention now turns to which Democrat will oppose her.

Chuck Schumer, the U.S. Senate Democratic leader, knew right away, naming Sara Gideon as his candidate immediately after her June 2019 announcement. She was given the Democratic Senatorial Campaign Committee list, and raised $7.6 million.

It wasn’t always like this. When Senate Democrats pulled off a “wave” election in 1986, picking up eight seats and gaining control, George Mitchell was campaign manager. The party always stayed out of primary fights, then put all its resources toward the winner.

Now, the DSCC tries to “manage” primaries, declaring a winner before voters have even focused on who’s running. Gideon has also racked up several national endorsements, including some — Planned Parenthood and the League of Conservation Voters — that once went to Collins.

But the game may not be over. Gideon, though serving two terms as House speaker, has never faced an electorate larger than her hometown of Freeport. As her predecessor, Mark Eves, learned when running for governor in 2018, a strong news presence doesn’t necessarily impress voters.

There’s another Democrat with the credentials, if not the money, to make a go of it. Betsy Sweet of Hallowell had a similar lack of experience when she ran for governor in 2018, while becoming the only Democrat to qualify for Clean Election funding.

Sweet honed her message, and finished a surprising third, ahead of Eves, the other progressive. She supports campaign finance reform, Medicare for All, the Green New Deal, and fair taxation for the rich — energizing issues for Democrats.

Gideon makes no such commitments, and temporizes on health care and the environment.

On taxes, she distinguished herself by giving away, unilaterally, the 2% income tax surcharge Maine voters enacted in 2016 — claiming that, if she hadn’t, Republicans would shut down state government; they did so anyway. Her decision was kept so secret many Democratic legislators knew nothing about it until an announcement by emissaries on what was supposed to the session’s final day.

Sweet has a lot of work to do, including distinguishing herself from former Google executive Ross Lajeunesse, who should have plenty of money. Yet there are signs her message is resonating.

A January survey through 2,000 phone contacts made by volunteers for Sweet’s campaign found her leading Gideon by 36% to 21%, with 42% undecided, and negligible support for any other candidate. Gideon’s support was almost entirely in Cumberland and York counties, and Sweet led almost everywhere else.

Polls don’t determine anything, but this one could be significant. It does show that Gideon’s $5 million in spending to date, against Sweet’s $217,000, hasn’t swayed many voters.

Against Susan Collins, a Democrat must show a clear contrast — on more than just the Trump issue — to have a serious chance. Democratic voters are intently focused this year, and so far only one candidate seems to be speaking their language.

Douglas Rooks, a Maine editor, opinion writer and author for 34 years, has published books about George Mitchell, and the Maine Democratic Party. He welcomes comment at: drooks@tds.net

(An earlier version of the column misrepresented the survey conducted by the campaign of Betsy Sweet. It’s been corrected.)