A string of recent court decisions in favor of Republicans has the GOP confident when it comes to battles centered on ballot harvesting, vote deadlines and other mail-in ballot issues.

While Democrats have been successful in some states, judges have lately been upholding existing state laws in the face of legal challenges that sought to expand allowances for mail-in voting.

PENNSYLVANIA DEMS SAY SUPREME COURT SHOULD LEAVE 3-DAY BALLOT DEADLINE EXTENSION, WARN OF DISENFRANCHISEMENT

"The RNC is protecting the vote by intervening against Democrats’ radical attempts to overhaul our election systems," Republican National Committee chairwoman Ronna McDaniel said in a statement. "We continue to win this battle in the courts, ensuring Americans can be confident in our elections, by stopping Democrat attempts to legalize ballot harvesting and count ballots received weeks after Election Day."

The latest ruling came when the Supreme Court on Monday rejected a lower court's attempt to force South Carolina to lift a witness requirement on absentee ballots. Democrats had sought to have the requirement put on hold because of the coronavirus pandemic, but Republicans had defended it as deterring fraud.

A federal appeals court also recently reinstated Georgia's Election Day deadline for receiving mailed ballots. A lower court had granted a three-day extension, but the Eleventh Circuit stayed the ruling pending appeal.

A push by the American Federation of Teachers to extend New Hampshire's deadline was similarly rejected by the state's superior court, Patch.com reported.

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In another case, a federal judge ruled Sunday that an Ohio mandate requiring that signatures on absentee ballots be verified should remain in place despite a legal challenge from voting rights advocates.

Last week, the Maine superior court dealt a blow to organizations and voters who were looking to relax state laws involving third parties turning in ballots and the state's Election Day deadline for receiving them. The judge said state interests – including the desire to prevent voter fraud – outweigh any burdens that may be imposed on voters.

The Supreme Court also said Friday that it would review a 2016 Arizona law dealing with third parties submitting ballots. That law prohibits anyone but a family member or caregiver from returning another person’s early ballot.

In January, a federal appeals court ruled that Arizona’s law banning so-called “ballot harvesting” violates the Voting Rights Act and the Constitution. Any further action has been stayed until the Supreme Court weighs in on the matter.

The Democratic National Committee did not immediately respond to Fox News' request for comment on the recent rulings.

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The Supreme Court has yet to issue a highly anticipated ruling on a case out of the key battleground state of Pennsylvania. The state supreme court granted a three-day extension to Pennsylvania's deadline for receiving ballots – which had previously been set as Election Day – as long as they are postmarked by Election Day. Republicans are looking to the high court to invalidate the ruling.

Fox News' Thomas Barrabi, Julia Musto, and the Associated Press contributed to this report.