BOSTON (SHNS) – Most members of the Massachusetts Senate would see their constituency shift under a draft redistricting map that would craft two new districts where non-white residents outnumber white residents.

The map that Senate Democrats unveiled on Tuesday would avoid pitting any sitting senators against one another in a chamber where Republicans hold just three seats currently, and it further shifts the state’s political center of gravity eastward in response to population trends highlighted in the 2020 U.S. Census.

It would also create two incumbent-free districts, including one aimed at empowering Hispanic or Latino voters in the greater Lawrence area who historically have had their voices diluted by white voters in neighboring communities.

Senate leaders praised their proposal for slashing the number of cities and towns split into multiple districts by half, but some reconfigurations generated criticism and one draw the threat of a legal challenge.

Sen. William Brownsberger, who co-chaired the special committee that crafted new lines based on the 2020 U.S. Census, said the median Senate district will shift about 20 percent from its existing shape.

The addition of two new majority-minority districts would bring the total number in the Massachusetts Senate to five, adding to two that already exist in the Boston area and one in the Springfield area.

The existing Senate is overwhelmingly white. Sen. Chang-Diaz, who is running for governor, and Sen. Adam Gomez of Springfield are the only two people of color in the 40-person chamber. Former Sen. Dean Tran, who came to the United States as a refugee from Vietnam, lost his re-election bid in November.

One of the two new majority-minority districts would feature Everett, Chelsea, Charlestown and eastern portions of Cambridge. That district today, represented by Everett Democrat Sen. Sal DiDomenico, also features parts of Boston’s West End and Allston-Brighton neighborhoods. Brownsberger said those precincts constituted “sort of an appendix that was hard to connect to the rest of the district,” and the newly proposed map would remove those to make the shape “more compact.”

The other new district where nonwhite residents would outnumber white residents constitutes all of Lawrence and Methuen, plus some downtown Haverhill neighborhoods that have substantial Hispanic or Latino populations.

Voting rights advocates pushed to remove Lawrence, where more than eight out of 10 residents are Hispanic, from its existing Senate district that also includes the mostly white communities of Andover, Dracut and Tewksbury.

“When you look at the voting patterns, you see that it’s very polarized,” Brownsberger said. “Hispanics vote for Hispanic candidates predominantly, and non-Hispanics vote for non-Hispanic candidates predominantly in that area. The (current) grouping of communities is such that the choice of the Hispanic voters is unable to get elected.”

Under the current map, Andover Democrat Sen. Barry Finegold represents Lawrence, while Sen. Diana DiZoglio represents the northernmost towns stretching from Salisbury to her hometown of Methuen. DiZoglio, a Democrat, is running for state auditor in 2022.

Brownsberger said slicing off a piece of Haverhill was the “only option” to create a Lawrence-area district where Hispanic or Latino voters did not have their political power weakened by neighboring communities, an ongoing trend that he said violates the Voting Rights Act.

But the decision to split that community drew blowback after local leaders and State House members previously called for the city to remain whole.

Rep. Andy Vargas, a Haverhill Democrat who is running for the Senate, called it “unacceptable to cut out the heart of Haverhill and segregate the most diverse precincts from the rest of the city.”

“While the motivations may be to empower Lawrence to elect a candidate of their choosing (as they should), it does not need to come at the expense of diluting the power of Latino residents of Haverhill who call our community home,” Vargas said. “It does not need to come at the expense of splitting Haverhill, making a growing Gateway City of more than 67,000 residents into a minority stakeholder in two Senate districts. It does not have to come at the expense of creating unwieldy maps with shockingly similar features of the original gerrymandered district.”

The draft plan would also reshape the Second Suffolk District currently represented by Sen. Chang-Diaz into a district where about half of the citizen age voting population would be Black.

Like the Lawrence-based district, Brownsberger said his team redrew that Boston district with a specific section of the Voting Rights Act in mind aimed at giving minority populations the ability to select a representative of their choice.

“Currently you have two majority-minority districts in Boston, but neither one of them is capable of electing the choice of the Black voters,” Brownsberger said. “We’ve rebalanced those two and also their relationship to the districts around them.”

The map would shift Chang-Diaz’s existing district to the south and east, excising some sections of Jamaica Plain and the South End with higher shares of white voters and adding Black vote clusters in Mattapan and Hyde Park.

Brownsberger said his team modeled the district’s proposed new shape based on past elections and found that it would allow Black voters to select a representative of their choice, remedying what he called another Voting Rights Act violation.

Boston’s Ward 16 would be split across two Senate districts under the proposal, a step that Rep. Dan Hunt said would “strongly dilute the city’s power.”

“We’re pursuing all legal options,” Hunt, who chairs the Ward 16 Democratic Committee, said in an interview. “Clearly, the adjacent precincts are communities of common interest, ethnically, in an urban mindset, socioeconomically. This break goes against the tenet to keep cities and towns whole.”

Overall, the new map would divide 10 cities and towns into multiple Senate districts: Boston, Worcester, Springfield, Chicopee, Cambridge, Winchester, Lexington, Braintree, Haverhill and North Andover. Of those, only Haverhill would be newly split.

Another 12 communities that stretch across multiple Senate districts on the current map would no longer be split: Clinton, Northborough, Northbridge, Franklin, Sudbury, Natick, Attleboro, Wellesley, Needham, Sharon, Easton and East Bridgewater.

Brownsberger and his counterpart on the House side, Rep. Michael Moran, said they are reaching out to municipal leaders in those cities and towns to address any issues.

Cities and towns traditionally drew their precincts before lawmakers created legislative districts, but the order flipped this year under a law Gov. Charlie Baker signed last week. Lawmakers said that order-of-operations switch responds to delays the COVID-19 pandemic inflicted on delivery of the U.S. Census data used in determining new political boundaries.

Voting advocates in the Drawing Democracy Coalition praised the increase in majority-nonwhite Senate districts while noting it fell short of their proposal to bump the number up to seven.

Beth Huang, director of the Massachusetts Voter Table and a leader in the Drawing Democracy Coalition, said the coalition’s goal for the Senate was to split Lawrence from Andover and create a district “weighted toward BIPOC communities, specifically Latinx communities, in the Merrimack Valley.”

“At the end of the day, the Senate district in the Merrimack Valley accomplished that goal,” Huang said.

Huang, however, said it was disappointing that Brownsberger and Senate leaders chose not to create a new majority-minority district that grouped Brockton with Stoughton and Randolph — communities the coalition considers to have similar interests. She also questioned the use of citizen voting age population to draw the Second Suffolk District in Boston.

Huang said the map would create an “overconcentration of Black voters” in that district and “weakened minority representation” in the First Suffolk District.

Brownsberger said he expects that advocates will “feel comfortable” with the Boston changes and the role that citizen voting age population played in decision-making once they reviewed the data.

He also said Senate leaders opted not to pursue another mostly nonwhite district anchored by Brockton because, unlike other parts of the state, the region did not have “an adequate population of any particular majority.”

Common Cause Massachusetts Executive Director Geoff Foster said the Senate’s proposal “would be stronger if total population was used to draw more majority minority districts.”

“Instead, we see low-income and communities of color in Brockton, Boston, and Haverhill who could suffer political consequences for a decade,” Foster said. “It is our hope that those community voices will be centered in the six-day public input period and as a coalition we will evaluate our options.”

Asked if protecting incumbents factored into decisions, Brownsberger replied that “continuity of representation is something we always factor” but added that “most senators are experiencing change.”

Only six of the Senate’s 40 districts — those currently represented by Sens. Patrick O’Connor of Weymouth, Mark Montigny of New Bedford, Jason Lewis of Winchester, Cindy Friedman of Arlington and Michael Rodrigues of Westport — are unchanged from the last decennial redistricting process.

For some senators, the updates would be more dramatic. Sen. Anne Gobi, the vice chair of the Redistricting Committee, would see her district slide to the east and fall entirely within Worcester and Hampshire counties. Brownsberger estimated more than half of her constituency would be new, calling it “a very heavy load for her to have to shoulder.” The district currently held by Sen. Barry Finegold, an Andover Democrat, would be more than two-thirds new to him, Brownsberger said.

With an eye on the one-year residency requirement to run for state representative, House and Senate leaders are aiming to wrap up the once-a-decade process of redrawing state legislative lines by early November.

The release of draft maps on Tuesday kicks off a public comment period that will last until 5 p.m. on Monday.

Lawmakers leading the redistricting push also need to craft new boundaries for the state’s eight Governor’s Council districts and nine congressional districts, which Brownsberger said would be released “shortly.”

“Exactly what shortly means, whether that’s a couple of days or a couple of weeks, we’re not sure yet,” he said.

[Matt Murphy contributed reporting.]