With less than a month to go before primary elections, contested races are heating up across Massachusetts.

The primary, scheduled for Tuesday, Sept. 4, will decide which Democratic and Republican candidates will go on to run against one another in the general election scheduled for Nov. 6.

This year, the primary is scheduled for the day after Labor Day, which could complicate voting for some people, such as families with school-age children and college students, who might be leaving the state.

“Voting on the day after Labor Day will prove challenging for voters in the commonwealth, especially for families preparing children for the start of school, and for candidates who are eager to get their message out to voters,” the League of Women Voters Massachusetts wrote in a statement earlier this year.

Aug. 15 is the deadline for voter registration, and absentee ballots must be received by local election officials by 5 p.m. on Aug. 31, according to the Secretary of State’s office.

Primary elections, as it is, typically draw fewer voters than general elections, especially in years without a race for United States president.

About 716,028 of eligible voters — 16.9 percent — cast ballots during the primary election in 2014, the most-recent midterm election, which is a far cry from the 2.2 million people who voted during the general election a couple months later.

The large number of uncontested primary races, too, could contribute to low interest among voters, especially in districts with few choices.

Statewide and congressional races are typically more competitive. But the parties are less successful in garnering much competition for legislative races.

For the 160 seats in the Massachusetts House of Representatives, there are 35 contested primary races for Democrats and five contested races for Republicans. In the state Senate, with 40 seats, there are six contested races for Democrats and zero for Republicans.

For statewide and regional races, Democrats will be paying close attention to contested races, including the U.S House of Representatives, governor, lieutenant governor, secretary of state and a few Governor’s Council seats.

Republicans, meanwhile, are eyeing contested races for U.S. Senate, U.S. House of Representatives, governor and attorney general.

Libertarians have no primary races and independents are only required to run in the general election.