By SCOTT BAUER, Associated Press

MADISON — A federal judge Tuesday blocked enforcement of a Wisconsin election law that's at the center of an investigation into Gov. Scott Walker's 2012 recall campaign and more than two dozen conservative groups.

U.S. District Judge Rudolph Randa granted the request to block the law from the Milwaukee-based group Citizens for Responsible Government Advocates while the conservative group's underlying lawsuit challenging its constitutionality goes forward.

The ruling allows candidates to coordinate and work closely with independent groups that don't explicitly tell people how to vote. Those groups frequently run television ads attacking or praising candidates, without saying who to vote for.

The conservative group CRG, which supports Republican Walker, argued that immediate action was needed because it wants to work with candidates — not including Walker — before the Nov. 4 election to create a website called "Take Charge Wisconsin!" but is fearful such coordination could be found to be illegal.

Randa, in agreeing to temporarily block enforcement of the law, said that time was of the essence with the election just three weeks away. Walker is in a tight race for re-election against Democrat Mary Burke. Democrats and unions unsuccessfully sought to recall Walker in 2012 after he pushed through a law sharply curbing the power of public sector unions in Wisconsin.

"Any further delay threatens to negate the effectiveness of CRG's requested relief," Randa wrote of the group.

Prosecutors have argued in court filings that coordination between a candidate and an outside group is illegal if it's done to influence the outcome of an election, even if the speech is focused on issues and doesn't advocate for or against any candidate.

Wisconsin prosecutors cited the campaign coordination law in launching a so-called "John Doe" investigation into Walker's campaign and at least 29 conservative groups. The conservative groups argue that such coordination is protected by the U.S. constitutional right to free speech.

A federal appeals court last month overturned a ruling from Randa in May that stopped the investigation, but also said the issue needs to be resolved in state courts.

The investigation remains on hold because a state judge overseeing it blocked the issuance of subpoenas. An appeal of that decision is pending before the Wisconsin Supreme Court.

Dan Kelly, a private attorney hired to defend the state elections board and Milwaukee County District Attorney John Chisholm — who launched the investigation of Walker's campaign and the others — declined to comment. Kelly was hired after Republican Attorney General J.B. Van Hollen declined to defend the law, saying he didn't agree with how state elections officials were interpreting it.

Kevin Kennedy, director of the Government Accountability Board, which supervises Wisconsin elections, said the board would discuss options with its attorney. Judge Randa gave them one week to respond.

The conservative group praised the ruling.

"Today's decision vindicates the right of all Wisconsin citizens to work with their elected representatives to advance shared policy goals," said David Rivkin, attorney for CRG.