When the two candidates in this year’s Massachusetts Senate race meet tonight at GBH for their first and only debate, the stakes will be high for both — but especially for Republican Kevin O’Connor, whose challenge to Ed Markey, the Democratic incumbent, features some daunting structural hurdles.

O’Connor, a Dover resident who attended Trinity College and Boston College Law School and is making his first bid for elected office, had hoped for more opportunities to contrast his candidacy with Markey’s. In mid-September, O’Connor stood outside the Malden Public Library — where Markey had celebrated his hard-fought primary win over Joe Kennedy — and called for seven debates, one more than Markey had with Kennedy.

“Senator Markey and I, as everyone knows, have substantive disagreements, and we live at a time of crisis,” O’Connor said at the time. “We deserve from our leaders, at a minimum, transparency and responsible dialog. Senator Markey has that opportunity in this election, and he has that obligation to the people of Massachusetts and the taxpayers of Massachusetts.”

In a recent interview, John Walsh, Markey’s campaign manager, cited the Senate’s fall schedule and the logistics of debate planning when asked about O’Connor’s proposal.

Walsh also noted that Markey’s debates with Kennedy took place over the better part of a year — and said the contrast between Markey and O’Connor is so stark that one debate is all voters really need.

“The differences between Joe Kennedy and Ed Markey might, [to] some people, seem fairly nuanced,” Walsh said. “They both supported the Green New Deal. They both supported Medicare for All … It’s not going to take long for people to see the difference between Ed Markey and Kevin O’Connor on all the issues.”

For example, Walsh said, O’Connor thinks the Senate should hold a vote this year on President Donald Trump’s Supreme Court nominee, Amy Coney Barrett. Markey doesn’t.

In addition, Walsh said, “It seems pretty clear [O’Connor] is not embracing any specific criminal-justice or police reforms, and is on attack on those things.”

On that point, at least, O’Connor would probably agree.

“Senator Markey has been on a sustained campaign to vilify our police officers,” O’Connor told GBH News. “He wants to defund the police.”

(During the Democratic primary, Markey called for “a rebalancing of the budget between policing and health care and education and other opportunities,” adding: “It is time for us to have that debate and to effectuate those changes in our society.”)

O’Connor contends that stance and other positions embraced by Markey — including expanding the Supreme Court and implementing the Green New Deal, which he co-wrote with New York Rep. Alexandria Ocasio-Cortez — put the senator outside the political mainstream, in Massachusetts and among Democrats.

“He is running statewide essentially as a Democratic Socialist,” O’Connor said of Markey. “He has hitched his wagon very publicly to the AOC and Bernie Sanders wing of the party.”

The flip side of that argument: O’Connor has hitched his wagon to Trump, whom he plans to vote for next month.

The president is not popular in Massachusetts. Four years ago, Hillary Clinton won 60 percent of the vote to Trump’s 33. This August, an Emerson College Polling survey showed Joe Biden, the Democratic nominee, leading Trump by a wide margin, 68 percent to 30 percent.

Shannon Jenkins, a political scientist at UMass Dartmouth, says Massachusetts’ low regard for the president is a major electoral liability for O’Connor.

“All the indications are that turnout will be up in this election cycle, even in Massachusetts, where we pretty much know the outcome,” Jenkins said. “Those people who are turning out in Massachusetts will most likely be voting for Biden and Harris … and most voters don’t really split their ticket.”

That tendency to vote the party line, Jenkins said, is especially pronounced when voters are relatively uninformed about down-ballot races — which brings up another big obstacle she sees looming for O’Connor.

“There is so much going on — there’s so much noise — that it is really hard for him to break through,” Jenkins said. “His challenge is to get his name out there, to get voters to recognize his name, and when there’s so much else going on, consuming the news cycle, it really is an uphill battle for him.”

What’s more, Jenkins says, O’Connor’s candidacy has two other significant factors working against it. Incumbents tend to win re-election — and in Massachusetts, where registered Republicans comprise less than 10% of the electorate, GOP congressional candidates rarely win. (The last Republican to succeed was Scott Brown, who was elected to the Senate in a special election in 2010 and lost his seat to Elizabeth Warren in 2012, the same year President Barack Obama won reelection.)

All of which raises a crucial question: Heading into the lone debate of this Senate contest, just how close is the race?

A recent poll released by the O’Connor campaign showed Markey leading by 10 points, 50 percent to 40 percent. But Steve Koczela, the president of the MassINC Polling Group, says those numbers should be viewed with a measure of skepticism.

Internal polls are “often released for a specific reason, whether because it’s the poll they’ve done during the course of the campaign that made the candidate look best, or [to] show donors that the race is close and they should donate,” Koczela said.

That particular poll, which was conducted by the Remington Research Group, also gave the president higher-than-usual marks in Massachusetts, putting his favorability at a relatively robust 37 percent. Fifty-three percent of respondents said they viewed Biden favorably.

“What you want to do with internal polls is compare them with other things you know, to see what that might be telling you,” Koczela said. “In this case, the other things that were in poll that you could use for comparison seemed to be tilting more to the right than one would expect from Massachusetts.”

The differences when it comes to campaign finance are clearer, and considerable. As of mid-August, shortly before his primary fight with Kennedy concluded, Markey had roughly $3.5 million cash on hand, despite spending $8.3 million since the beginning of 2019 — spending that likely boosted his public profile. O’Connor, in contrast, had about $125,000.

Whatever the current state of play really is, Walsh, Markey’s campaign manager, insists the incumbent is not taking his challenger lightly.

“Kevin O’Connor is a credible candidate,” said Walsh. “He is a smart, highly educated, articulate representative of a philosophy that is different than Ed Markey’s.”

For his part, O’Connor seems to relish his role as a perceived long shot.

“I think the state of the race is very favorable,” O’Connor said. “I’m the underdog, as everyone expected. … People want a common-sense candidate, and I believe I offer that.”

Tonight’s debate will be televised on GBH 2 and simulcast across the Commonwealth on 89.7, CAI, WGBY, NEPR, and streaming on Zoom, Facebook, Twitter, and YouTube.
The post-show analysis hosted by Joe Mathieu will air on 89.7 and stream on Zoom, Facebook, Twitter and YouTube.