(CNN) -- The Supreme Court refused Monday to reconsider one of its most controversial decisions of recent years, which has had a dramatic effect on election campaigns.

In a 5-4 ruling, with the more liberal justices dissenting, the high court refused to hear arguments over whether a state can limit campaign spending by corporations.

The case focused on Montana, but its implications were widespread.

In a nutshell, the court decided that its 2010 Citizens United decision -- which helped open the floodgates to massive corporate spending in elections and give birth to super PACs -- trumps state laws. And it won't be revisited any time soon.

That ruling blessed unlimited campaign spending by corporations, saying they have the same free speech rights as wealthy individuals, who have long enjoyed the ability to spend freely on behalf of federal candidates.

The central question in the Montana case was whether a state can maintain its own laws limiting independent campaign spending.

Montana's highest court ruled that the state can keep its own century-old restrictions. In February, the U.S. Supreme Court blocked enforcement of that state ruling.

The question before it now was whether to hear arguments from both sides.

In its ruling Monday, the court said, "The question presented in this case is whether the holding of Citizens United applies to the Montana state law. There can be no serious doubt that it does."

Justice Stephen Breyer wrote the dissenting opinion, joined by Justices Ruth Bader Ginsburg, Sonia Sotomayor, and Elena Kagan.

Breyer wrote that he disagreed with the Citizens United decision. And, he said, even if he had accepted it, Montana should be allowed to decide "that independent expenditures by corporations did in fact lead to corruption or the appearance of corruption in Montana."

Senate Republican Leader Mitch McConnell of Kentucky praised the court's decision Monday as "another important victory for freedom of speech."

He added, "Clearly, the much predicted corporate tsunami that critics of Citizens United warned about simply did not occur.'

Records showed that the vast majority of the money that went to eight super PACs supporting Republican candidates earlier this year came from individuals, while only about 14% came from corporations, he said.

McConnell had filed an amicus brief in the case.

House Minority Leader Nancy Pelosi slammed the Supreme Court's "terrible decision," tweeting that it "will keep floodgates open to special interest money."

The reform group Common Cause, meanwhile, issued a statement saying, "By summarily rejecting Montana's law banning corporate political spending, the Supreme Court has turned a blind eye to political corruption and the tsunami of special interest money flooding into this year's national elections."

It called the court's refusal to grant a hearing "arrogant."