Australia's High Court rejected a challenge to reforms to Senate voting on Friday in a boost for Prime Minister Malcolm Turnbull ahead of elections on July 2.
Legislators passed the reforms in March, making it harder for smaller parties to enter parliament through vote-sharing deals.
Should Turnbull be returned as prime minister, the verdict clears the path after several years of key policies being rejected by the upper house.
Independent and minor party senators elected at the last election in 2013 have stalled key aspects of the government's agenda, including changes that would make higher education and health care more expensive and limit access to welfare.
The government is running neck-and-neck in opinion polls with the centre-left Labor opposition, a sharp turnaround from Turnbull's honeymoon period, during which he was one of the most popular leaders in Australian history.
Turnbull still faces a gloomy economic outlook and Australia's hard-line immigration policy has drawn criticism at home and abroad.
The voting reforms were challenged by independent Senator Bob Day.
"The hurdle of getting elected to the Senate will be so high, they will never succeed," Day told reporters in Canberra. "That is anti-democratic."