The U.S. Supreme Court declined Monday to reopen a long-stalled investigation into Wisconsin Gov. Scott Walker's 2012 campaign against a recall effort, permanently ending a probe that had dogged the Republican even as he launched a brief presidential bid last year.

Prosecutors looking to revive an investigation into Republican Gov. Scott Walker's recall campaign have asked the U.S. Supreme Court to vacate a state decision halting the probe.

Wisconsin prosecutors have asked the U.S. Supreme Court to overturn a state Supreme Court decision that shut down an investigation of alleged coordination between Gov. Scott Walker's campaign and conservative groups.

The Wisconsin Supreme Court has allowed three district attorneys to appeal to the U.S. Supreme Court over a closed, secret investigation into whether Gov. Scott Walker's campaign illegally coordinated with conservative groups during the 2012 recall election.

The state Supreme Court has granted three prosecutors' request to join a case challenging an investigation into Gov. Scott Walker's campaign.

Three prosecutors filed a motion Friday to intervene in a court case halting a secret investigation into Gov. Scott Walker's recall campaign.

Court filings made public Wednesday related to the John Doe investigation into Gov. Scott Walker's recall campaign and conservative groups show prosecutors sought to keep the probe secret to avoid publicity, which they feared could hinder or taint their work.