Cook Political Report on Thursday moved seven US House races in Democrats’ favor, as Republicans fight to defend their majority in the chamber ahead of the November election.

The nonpartisan election forecaster adjusted its ratings in seven congressional contests, six of which are currently held by Republicans.

Erin Covey, the publication’s House editor, said Democrats remain well-positioned to compete for control of the House despite Republican efforts to improve their prospects through redistricting.

“Democrats remain in a strong position to regain control of the House, with the battlefield continuing to shift in their favor as the political environment further deteriorates for the GOP,” Covey wrote.

She added that several districts previously viewed as secure for Republicans are becoming increasingly competitive.

“Districts that once appeared to be relatively safe for Republicans look increasingly competitive,” Covey wrote.

Among the changes, Cook moved the race of Rep. Chuck Edwards, R-N.C., from likely Republican to lean Republican. Rep. Brad Finstad’s Minnesota district shifted from solid Republican to likely Republican, while Rep. Bill Huizenga’s Michigan seat moved from likely Republican to lean Republican. The race involving Rep. Max Miller, R-Ohio, was downgraded from solid Republican to likely Republican.

Two open Republican-held seats also became more competitive under Cook’s revised ratings.

Iowa’s 2nd Congressional District, currently represented by Rep. Ashley Hinson, R-Iowa, was moved from likely Republican to lean Republican. Hinson is seeking to succeed retiring Sen. Joni Ernst, R-Iowa. Earlier this month, former state Rep. Joe Mitchell won the Republican primary to replace Hinson on the ballot.

South Carolina’s 1st Congressional District, currently held by Rep. Nancy Mace, R-S.C., was shifted from solid Republican to likely Republican. Mace finished fifth in South Carolina’s Republican gubernatorial primary. Charleston County Councilmember Jenny Honeycutt and state Rep. Mark Smith are scheduled to compete in a Republican runoff on June 23 to determine the party’s nominee.

The lone Democratic-held seat affected by the changes was Alabama’s 2nd Congressional District, represented by freshman Rep. Shomari Figures. Cook moved the race from solid Republican to likely Republican, reflecting the challenges Figures faces after Alabama lawmakers redrew the district.

The updated ratings come as Republicans hold a slim advantage in the House, with a 218-212 edge. Independent Rep. Kevin Kiley of California caucuses with Republicans.

Four House seats are currently vacant, three of which were previously held by Democrats. If both parties retain those seats in upcoming special elections, Republicans would hold a 220-215 majority.

Under that scenario, Democrats would need a net gain of three seats in November to reclaim control of the chamber after spending two consecutive Congresses in the minority.

According to the Cook Political Report, only 18 of the nation’s 435 House races currently fall into the “toss up” category. Fourteen of those competitive districts are held by Republicans.