Florida’s Republican-dominated state legislature has approved a new congressional map, the latest salvo in an unprecedented national battle of redistricting before the midterm elections in November.

The vote in both the Florida state Senate and House on Wednesday comes just days after Florida Governor Ron DeSantis unveiled the new map, which heavily favours Republicans.

Currently, 20 Republicans and eight Democrats represent the state in the US House of Representatives. The new map puts Republicans on track to take 24 seats in the midterms, with four expected to go to Democrats.

It is a significant shift in the run-up to the consequential election, in which Democrats are considered favoured to retake control of the US House of Representatives and are also pushing – in a longer shot attempt – to take control of the US Senate.

A Democratic majority in either chamber of Congress would serve as a major check to US President Donald Trump in the final two years of his second term.

Questions remain about whether the new map is legal under the Florida Constitution, with legal challenges expected.

Some have also argued that redrawing the map may actually backfire on Republicans, diluting the party’s strongholds and tightening margins at a time when US President Donald Trump’s approval has dipped to an all-time low amid the economic knock-ons of the US-Israel war with Iran.

Some have seen the victory of Democrat Emily Gregory in a race for a state legislative seat representing Palm Beach – home to Trump’s Mar-a-Lago resort – as an early harbinger of Republicans’ looming electoral woes.

Several Democrats in the state legislature condemned the new map in advance of its passage on Wednesday.

“Y’all are doing this because y’all’s daddy in the White House is injecting national political objectives into what should be a state-driven process,” State Representative Michele Rayner told Republicans before the vote, referring to Trump.

Redistricting battle

The map is the latest strike in a redistricting battle that has swept the country, beginning last year with Trump pressuring Texas to redraw its legislative map to favour Republicans.

After the Republican-controlled legislature approved a new map expected to net Republicans an additional five seats, several other states followed suit, including Missouri, North Carolina, Ohio, California, Utah and most recently Virginia.

The process has brought the issue of gerrymandering, in which legislative maps are drawn to benefit one political party over the other, to the forefront of US politics. Voting advocates have long called for a series of reforms to prevent gerrymandering, including creating non-partisan commissions to oversee redistricting.

Trump’s early pressure on Texas – and the domino effect of redistricting – represented a departure from a longstanding norm of redrawing maps every 10 years following the US census population count.

Virginia’s vote last week, in which Democrats were expected to net four seats, largely neutralised Republican redistricting gains. Florida’s new map again gives Republicans the edge in seats gained in the redistricting flurry.

Still, Democrats are seen as having an advantage over Republicans in the November legislative elections, despite the tightening margins.

Florida’s vote comes after the US Supreme Court ruled that a Congressional map in Louisiana, previously redrawn to include two Black majority districts, was unconstitutional.

The ruling by the conservative-dominated panel represented a major blow to the 1965 Voting Rights Act, reinterpreting a provision meant to protect against officials drawing congressional maps to dilute the electoral power of minority groups.

Section 2 of the law has long been interpreted to prohibit drawing electoral ⁠maps that would result in diluting the electoral power of minority voters, even without direct proof that the maps had been drawn with racist intent.

The Supreme Court ruling said challengers must now prove racist intent to challenge such a map.

The ruling is relevant to Florida, as the state’s new map effectively eliminates one majority-Black southern Florida district represented in the US House by Sheila Cherfilus-McCormick, a Democrat who resigned earlier this month.

Black voters have historically aligned with Democrats.

The Supreme Court ruling could open the door for more states to revisit their congressional maps, though it remained unclear whether any would seek to do so with the midterm primary season already well under way.