PARIS (AP) – One month after President Emmanuel Macron’s arrival in power, French voters must now choose lawmakers in parliamentary elections starting Sunday that may dramatically reshape the political landscape.

Here’s a look at the French system and what’s at stake:

ELECTION RULES

Elections for the National Assembly are organized in two rounds on June 11 and June 18. All 577 seats are up for grabs, and each winner will serve a five-year term.

To win in the first round, candidates need an absolute majority and support from at least a quarter of the district’s registered voters. Otherwise, all contenders who get at least 12.5 percent of the votes of registered voters advance to the second round.

Most races involve several candidates in the first round and are whittled down to two in the second round.

In some races, three or four people will make it to the second round, though some may step aside to improve the chances of another contender. That tactic has often been used to block candidates from Marine Le Pen’s far-right National Front party.

In the second round, the candidate with the most votes wins. In the rare case of a tie, the older candidate wins.

The French Parliament is made up of two houses, the National Assembly and the Senate. The National Assembly always has the final say in the voting process of a law.

MACRON’S CHALLENGE

Macron, France’s youngest-ever president, is seeking an absolute majority in the Assembly to be able to implement his promised pro-business labor reforms and tougher security measures.

His year-old centrist political movement, Republic on the Move, is presenting candidates in 525 districts. Half are women, and many are newcomers in politics. Their average age is 47, compared to 60 for the outgoing assembly.

According to the latest polls, Republic on the Move could win as many as 400 seats, crushing mainstream parties and leaving no single opposition force.

OTHER PARTIES

Candidates from the conservative Republicans party are expected to arrive in second position, with possibly over 100 seats, opinion polls suggest.

The Socialist Party, which dominated the outgoing Assembly, is set to face significant defeat, with only a few dozen seats and many candidates eliminated in the first round.

The National Front is expected to do better than its two seats in the last legislature, with polls hinting it could win its highest-ever score with more than 10 seats.

But that still won’t be enough to make it the leading opposition force, as Le Pen had hoped after her strong second-place showing in the presidential race. Le Pen herself is running for a seat in Henin-Beaumont in northern France.

The far-left party of Jean-Luc Melenchon could obtain between 10 and 20 seats.

WHAT’S NEXT

Macron’s new prime minister, Edouard Philippe, and 22 government members are already drafting laws but need a new parliament in place to vote on them.

The government has announced legislation to clean up corruption and nepotism in politics, a major reform of worker protections, a bill to extend the state of emergency until November and another one to introduce permanent security measures.

If he doesn’t have a majority at the National Assembly, Macron may come under pressure to reshuffle his government and choose a prime minister from the winning party, a situation called “cohabitation.” That appears unlikely, given French voters’ disaffection with traditional parties.