Washington (CNN) -- Senate Republicans narrowly blocked Democratic campaign finance disclosure legislation in the Senate Tuesday after raising concerns the bill would curb freedom of speech and tilt campaign spending in favor of the Democrats. A 57-41 vote fell short of the 60 votes needed for the Senate to cut off debate on the measure. Republicans unanimously opposed the measure while Democrats solidly backed it. Democrats said the legislation -- known as the DISCLOSE Act -- would bring greater transparency to campaign contributions from corporations, labor unions, and other special interests, which were able to ramp up political spending in the wake of the Supreme Court's controversial ruling in Citizens United vs. Federal Election Commission earlier this year.
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NEW: Republicans accuse Democrats of an "assault on the First Amendment"
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The Senate GOP stops Democrats from ending debate on a campaign finance bill
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The bill would require groups paying for ads to disclose their top donors in the ads
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Democrats claim the bill is necessary to reduce the impact of a Supreme Court ruling
@placeholder denied that was their motive, and made certain changes to the bill last week aimed at satisfying GOP critics.