Democrat Edward J. Markey leads his Republican rival, Gabriel E. Gomez, by 20 points among likely voters five days before the special US Senate, according to a new poll.

Markey leads Gomez 56 percent to 36 percent, with seven percent of respondents undecided, according to the UMass Lowell-Boston Herald poll released this evening.

Among the broader group of registered Massachusetts voters, Markey leads by 21 percentage points, 53 percent to 32 percent, according to the poll.

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The poll surveyed 608 Massachusetts registered voters of whom 312 were considered likely to vote in the election. The survey, conducted by telephone from June 15-19 and had a margin of error of plus or minus 5.6 percentage points among likely voters and plus or minus 4 percentage points among registered voters.

A Boston Globe poll of likely special election voters conducted last week found Markey leading Gomez by 13 points. It had a margin of error of 4.3 percentage points.

The UMass Lowell-Boston Herald poll also tested the favorability of a number of political figures in the state.

Among registered voters, 63 percent of those surveyed have a favorable view of both Governor Deval Patrick and US Senator Elizabeth Warren. Twenty-six percent have an unfavorable view of Warren, while 21 percent have an unfavorable view of Patrick. Both are Democrats.

Forty-nine percent have a favorable view of former Senator Scott P. Brown, a Republican who has not ruled a future bid for higher office. Thirty-one percent have an unfavorable view of Brown, who lost to Warren in November.

Two potential 2014 candidates for governor, Republican Charles D. Baker, the GOP nominee who lost to Patrick in 2010, and Democratic state Treasurer Steven Grossman are not well-known statewide, the poll found.

Seventeen percent have a favorable view of Baker, while 14 percent have an unfavorable view of him. Fourteen percent have a favorable view of Grossman, while 12 percent have an unfavorable view of him.

The US Senate special election to replace former Senator John F. Kerry is set for June 25. The race for governor is set for Nov. 4, 2014.