Swiss voters are casting ballots to elect their parliament and polls show a nationalist party could advance amid widespread concerns about the recent influx of migrants into Europe.

Under Switzerland's arcane, multiparty system that favors stability, the election to two houses of parliament is unlikely to dramatically shift the current broad coalition government policy — even if the nationalist Swiss People's Party advances.

The latest poll by gfs.bern agency for the national broadcaster suggested the People's Party would win about 28 percent, the Social Democrats some 19 percent and the conservative Free Democrats just under 17 percent.

Despite early-voting and mail-in balloting options, polls suggest only about half of registered voters will cast ballots. They already have an important say in government policy because Switzerland regularly holds referendums.