Today, voters across the city and area will decide the fates of four local, liberal stars in two key primary races, for local state representative and senator.

Eyes across the state are watching the hotly contested race for a state senate seat in Cambridge and several smaller nearby towns, which pits former Cambridge Mayor Anthony D. Galluccio against popular state representative Jarrett T. Barrios.

But across town another race has shaped up with its own potential to make or break the political career of a homegrown pol. Paul C. Demakis ’75, the incumbent state representative from Boston’s Back Bay, faces a tough challenge from upstart candidate and Cambridge City Councillor Marjorie C. Decker.

Like the Galluccio-Barrios battle, this one has seen the candidates nearly indistinguishable on most of the issues, and the contests have instead have been more about personality than politics. And since neither race has any independent or republican contenders, the winners today will almost certainly be the victors come November.

The struggle, in each race, has been to prove liberal stripes while appealing to a broad swath of people. The senate seat for which Galluccio and Barrios vie, along with relative unknown Carlos DeMaria, contains Cambridge’s wealthier neighborhoods as well as several nearby blue-collar towns.

Similarly, the district for which Decker and Demakis struggle—newly redrawn—is about evenly split by the Charles River. It contains Boston’s tony Back Bay and Beacon Hill neighborhoods but 45 percent of the district falls in Cambridge’s more blue collar areas.

The battles will be all the tougher to call given the gubernatorial race’s potential to motivate unusually high turnout, according to Cambridge political observer Robert Winters. The governor’s race, which has heated up in recent weeks, will probably inspire more voters to take a stand on one of the four big local names, he said.

“For a while, honestly, I thought that the governor’s race was becoming so hopelessly boring that voter turnout would be low,” Winters said. “Now, it’s sort of like, aren’t you going to the game?”

In the Demakis-Decker race, the local names have gone beyond the political. Decker, who is young, progressive and well-funded, recruited the support of hometown boys turned movie stars Matt Damon and Ben Affleck. Damon recorded an answering machine message pitching her candidacy and Affleck endorsed her in campaign literature.

Decker says she hopes to work on issues of what she calls “social health” in the state—improving health care and education and lessening income inequality in Massachusetts.

Decker, who is only 30 years old, already has developed a campaign machine that catapulted her to strong showings in two city council races. And as a Cambridge figure she is expected to benefit from the higher voter turnout usually seen on her side of the Charles River.

But Demakis has a well-established name and a reputation for success on issues such as creating buffer zones outside of health clinics that perform abortions and preventing Boston University from building a sailing pavilion on choice property along the Charles.

He’s won several key endorsements from both sides of the river, including nods from the Globe and Herald and the Boston NOW chapter. He has also garnered support from former Cambridge Mayor Francis H. Duehay ’55, a longtime and well-known presence in local politics.

While Demakis is often noted as a foe of House Speaker Thomas Finneran—one of only 14 Democrats, he says, who voted for a term limit that would have ousted the powerful house leader—Decker has charged that Demakis has sided with Finneran too often.

The redistricting that pushed Demakis’ district further into Cambridge became controversial in the city, since it split a traditionally-minority district. According to Decker, Finneran arranged for the change in part as a favor to Demakis.