A week after the election, many House and two Senate races are undecided.

A week after Election Day, ballots are still being counted in many states. This isn’t unusual. But because so many people voted by mail this year, the process isn’t as far along as it would normally be.

Aside from the presidential contest in four states — Arizona, Georgia, North Carolina and Alaska — two Senate races and 16 House races were unresolved as of Tuesday evening. That’s in addition to planned runoffs for Georgia’s two Senate seats and a Louisiana House seat in the coming months.

These are some of races we’re watching:

  • Alaska: The Republican incumbents Senator Dan Sullivan and Representative Don Young both hold substantial leads.

  • California: Four House races remain uncalled. The closest include one in the San Joaquin Valley, where Representative T.J. Cox, a Democrat, trails former Representative David Valadao, the Republican, by about 4,500 votes, and one north of Los Angeles where Representative Mike Garcia, a Republican, trails Christy Smith, a Democrat, by about 1,300 votes.

  • Illinois: Representative Lauren Underwood, a first-term Democrat, has pulled narrowly ahead of her Republican challenger, Jim Oberweis, in Chicago’s western suburbs.

  • Iowa: One of the nation’s closest House races is in the Second Congressional District, which covers the southeast part of the state. Just 42 votes separate Rita Hart, a Democrat, from Mariannette Miller-Meeks, a Republican.

  • New York: Eight House races, including some that are not close, remain uncalled because New York has been slow to start counting mail ballots. Close ones include the 18th District in New York City’s northern exurbs, where Representative Sean Patrick Maloney, a Democrat, leads his Republican challenger, Chele Farley, by just over two points, and District 19 in the Hudson Valley, where Representative Antonio Delgado, a first-term Democrat, is narrowly ahead of his Republican challenger, Kyle Van De Water.

  • North Carolina: The Republican Senator Thom Tillis is narrowly ahead of his Democratic challenger, Cal Cunningham. Mr. Cunningham conceded on Tuesday, but The Times has not officially called the race.

  • Utah: Representative Ben McAdams, a Democrat whose 2018 victory was one of the biggest upsets of the midterms, trails his Republican challenger, Burgess Owens, by less than half a percentage point.