The Cook Political Report, a closely watched election forecaster, moved 18 U.S. House races toward Democrats on Friday.

All 18 changes favored Democrats. Cook now says the most likely result is that Democrats pick up nine to 19 seats, which would give them between 224 and 234.

Several Republican-held seats moved from toss-up to leaning Democratic, including Rep. Mariannette Miller-Meeks' race in Iowa against Democrat Christina Bohannan, Axios reported. Four races in Iowa, Michigan, North Carolina and Virginia moved from leaning Republican to toss-up. That helps Democratic Rep. Don Davis of North Carolina, whose district was redrawn. Seats in Kentucky, Maine, Pennsylvania, Arkansas and Indiana also slipped for Republicans.

Cook said heavy Republican ad spending "has yet to move the needle." It wrote that GOP candidates are struggling "to free themselves of the anchor of President Donald Trump."

Republicans pushed back. "House races are won in the districts, one by one, with battle-tested candidates and messages that work," National Republican Congressional Committee spokesman Mike Marinella told Axios. "In November, we're going to win."

Cook rates 21 races as toss-ups. Republicans hold 15 of them and Democrats hold six. Democrats would need to win only about one in five of those toss-ups to take a majority, if the other seats go as rated, Axios reported.

The forecast lands as Trump travels the country to campaign for Republicans. A Politico poll out the same day found about a quarter of 2024 Trump voters think local GOP candidates would do better by breaking with him.

Election Day is November 3.

What we know: Cook expects Democrats to win the House.
What we don't: Whether late spending or turnout changes the picture.