Looking to gauge the chances Rep. Stephen Lynch will upset front-running Rep. Ed Markey in the Massachusetts Senate Democratic primary? Take a peek at the GOP primary.

Rep. Stephen Lynch (Charles Krupa/AP)

Yes, the Republican primary. A new WBUR poll out Friday showed Markey leading Lynch by just seven points among those likeliest to vote in the special Democratic primary, 38 percent to 31 percent. Lynch's success in the poll is due in large part to strong support among unaffiliated voters, who can participate in either primary. And where they decide to cast their ballots could make the Democratic race much more or much less competitive.

“One of the interesting things about the Democratic primary is it could actually be affected by the Republican primary, and what I mean by that is that where unaffiliated voters vote on primary day actually will affect the Democratic primary,” MassINC pollster Steve Koczela told WBUR. MassINC Polling Group conducted the WBUR survey.

Indeed, Lynch's fate may well rest, at least in part, on how many independent voters he can turn out in the Democratic primary. In the WBUR poll, Markey leads Lynch by 17 points among Democrats, but trails by four among independent voters.

A number of Republicans have declared their intention to run in the special election. But until the Feb. 27 deadline for submitting 10,000 valid signatures comes and goes, we won't know how crowded the field will be. An active and competitive primary that attracts a lot of interest would be bad news for Lynch.

The live-caller WBUR survey stands in contrast to a recent poll from Democratic automated pollster Public Policy Polling, which showed Markey leading Lynch by a much wider 52 percent-to-19 percent margin. A Lynch aide attributed his strength in the WBUR poll to a message that aligns with voters' priorities. "I think the poll reflects what people are looking for," strategist Scott Ferson said.

To be clear, getting enough independents to take an interest in his candidacy could be a tall order for Lynch. And it still may not be enough, considering Markey's clear upper hand on the left.

The more liberal congressman is backed by the Democratic Senatorial Campaign Committee and Secretary of State John Kerry. This week, Markey also landed the endorsement of the Massachusetts Teachers Association -- a blow to Lynch, who's built his political career with strong support from organized labor. Markey is also expected to have more money to spend once the advertising war begins and will have numerous high-profile Democratic surrogates on his side.

"This race is about who will be the passionate voice for the families and future of Massachusetts, and Ed is focused on the issues that matter most to voters -- creating jobs, standing up for working families and fighting the special interests," said Markey spokeswoman Giselle Barry.

Lynch is more conservative than Markey on a number of matters, but appears to be trying to recast his image on divisive social issues. Take abortion, for example. Over the years, Lynch has described himself as an antiabortion rights Democrat. But he recently said abortion is a constitutionally protected right and that he would oppose anti­abortion nominees to the Supreme Court in the Senate, the Boston Globe reported.

Lynch has been making the case to Democratic primary voters who like his economic message that his views on social issues are acceptable, Ferson said.

In a nutshell, it’s too early to judge how close this race really is, with limited polling and no real air war to speak of yet. The early indications are that Lynch has a chance, but still has his work cut out for him.