May 31 (Reuters) - The U.S.

Supreme Court this year already has given a boost to President Donald Trump and his fellow Republicans in the nationwide battle over redrawing electoral maps.

In the coming weeks, it could rule in favor of the Republicans in two more significant cases related to elections ahead of the November elections that will decide control of Congress.

In a case from Mississippi, Republican Party officials are seeking to strike down state laws that allow late-arriving mail ballots to be counted as long as they are postmarked by Election Day.

Trump has sought to cast doubt on the security of mail-in ballots, though evidence of voter fraud is rare, and Democratic voters tend to use this mode of voting more than Republicans.

In a separate case involving Trump’s Vice President JD Vance, Republicans are seeking to further chip away at legal limits on money in political campaigns - specifically involving spending coordinated between party organizations and candidates.

They argue such curbs violate the U.S.

Constitution’s First Amendment protections against government abridgment of freedom of speech.

The court has proven receptive to such an argument, including in its landmark 2010 decision in the case Citizens United v.

Federal Election Commission.

Rulings in both cases are expected by around the end of June.

Republicans are defending slim majorities in both the House of Representatives and Senate in the November 3 midterms.

If Democrats win control of either chamber, they could impede Trump’s legislative agenda and mount investigations of him and his administration.

VOTING RIGHTS CASE RULING The Supreme Court has a 6-3 conservative majority.

In an April decision powered by the conservative justices in a case from Louisiana, it gutted a key provision of the Voting Rights Act, making it harder to challenge electoral maps as racially discriminatory under the landmark civil rights law.

That decision provided an immediate advantage to Trump’s party ahead of the midterms, though legal experts said the impact of the two forthcoming rulings is harder to gauge.

The Voting Rights Act ruling opened the door for Republican state legislators to dismantle Democratic-held U.S.

House districts with large Black or Latino populations across the South, potentially giving Republicans an electoral advantage for years to come.

Black and Hispanic voters tend to vote for Democratic candidates.

That decision has been a “boon for Republicans,” said Travis Crum, a Washington University in St.

Louis School of Law professor.

Thanks in part to that ruling, Republicans are positioned in November to gain up to a dozen U.S.

House seats currently held by Democrats through the process of redistricting - redrawing the boundaries of voting districts.

Working against Republicans in November are Trump’s sagging approval ratings, as measured by public opinion polls, amid the unpopular Iran war and the higher gasoline prices it caused, and the historical trend of a president’s party losing congressional seats in midterms.

CAMPAIGN FINANCE CASE Vance and other Republicans appealed a lower court’s ruling that upheld restrictions on the amount of money parties can spend on campaigns with input from candidates they support - called coordinated party expenditures.

Vance was running for the U.S.

Senate in Ohio in 2022 when he and other challengers sued.

Under the bedrock 1971 law regulating fundraising in U.S.

federal elections, spending by a political party to advocate for or against a candidate that is not coordinated with a candidate’s campaign is considered an independent expenditure not subject to amount limits.

But it does restrict contributions coordinated between a party and a campaign.

Supporters of these restrictions have said they help prevent corruption.

Without them, they said, wealthy donors could curry favor with candidates by routing massive sums to them through political parties, evading limits on how much any individual can donate to a candidate....