The U.S. Senate voted Wednesday to block a change to labor laws that would make it easier for workers to form a union.

The 53-46 vote was mostly along party lines, with no Democrats voting to block the law and only one Republican, Sen. Lisa Murkowski (R-AK), voting with Democrats and Independents to let the law stand.

The change to National Labor Relations Board (NLRB) law streamlines the process for private sector workers to vote on whether to join a union. It also reduces, from a median of 38 days to 11, the typical time between a union’s request for representation and the vote by workers on whether to form a union.

Labor advocates say this is necessary to reduce anti-union intimidation by employers. A 2011 study by labor researchers at the University of California, Berkeley, found that the longer union elections are delayed, the more unfair labor practice complaints workers file against their employers.

This is because the longer delay gives employers more time to intimidate workers with tactics such as “captive audience” meetings to discourage employees from joining a union.

Furthermore, employers have tremendous power to delay the timing of a union election. Simply by demanding a pre-election hearing, employers can delay elections by a hundred days or more, leaving even more time to subject workers to anti-union campaigns.

“Too often, lengthy and unnecessary litigation over minor issues bogs down the election process and prevents workers from getting the vote they want,” AFL-CIO president Richard Trumka said when the rule was issued in December.

Republican opponents of the rule change called it an “ambush election rule,” alleging that it gave employers too little time to respond to a union request and employees too little time to learn the facts.

To block the rule using a simple majority, Republicans invoked the Congressional Review Act, a seldom-used relic of the Newt Gingrich era that allows Congress to overrule new federal regulations issued by government agencies.

The resolution of disapproval has to be passed by both chambers of Congress and signed by the president. It’s likely to pass the Republican-dominated House, but Obama has resolved to veto it.

“Trying to make government work better shouldn’t be controversial. But it is controversial. Why? Because some employers simply oppose union votes all together,” Sen. Elizabeth Warren (D-MA) said on the Senate floor. “They don’t want the NLRB to work—they don’t want union elections to happen at all—so they are lobbying against these new rules. And Congressional Republicans are standing up for them.”

Research shows that the decline in union participation since the New Deal has corresponded with rising inequality in the United States.