Last week's Supreme Court decision to allow corporations and unions to spend unlimited sums directly from their treasuries on political speech — including advocacy for or against candidates — should be a strong warning to voters: The influence of big money over elections, already large, is poised to expand dramatically.

The 5-4 ruling in Citizens United v. Federal Election Commission cast aside decades of precedent and efforts by legislative bodies to restrict the power of corporate interests to unduly influence federal elections.

Giving full First Amendment freedoms to corporations, as if they were individuals, creates the potential for candidates to be either propped up or preempted by massive blasts of electioneering, right up to election day.

However one feels about this expansion of free speech — and First Amendment absolutists on both the left and right praised the decision — the possible consequences demand a response.

A key line of defense against abuse are laws governing disclosure and transparency in campaigning, which thankfully the high court left intact in the Citizens United case. "Disclosure is a more effective tool than anyone realizes" to deter improper behavior, says Daniel Mollway, executive director of the state Ethics Commission.

He's right. And campaign disclosure laws should make it as easy as possible for the public to know who's behind campaign spending — whether for corporate-sponsored political advertising that will flourish under Citizens United, or other types of the campaign spending, like direct donations to candidates or political action committees. One good idea: Change federal law to require political expenditures to be reported immediately on the Internet, rather than quarterly.

Hawai'i state law already allows corporations free rein to express political opinion on their own, but it restricts how they donate to candidates and PACs. These laws should be strengthened to give the public better access to detailed and up-to-date reports on who is donating to whom. Several proposals from the state ethics and campaign spending commissions are being weighed by state lawmakers and are worthy of consideration. Among them:

• Require lawmakers to file financial disclosure forms in January, not after the session ends.

• Increase lobbying disclosure reports from three to four times a year.

• Reduce the threshold for gifts disclosure from $200 to $50.

• Require complete financial interest forms to be filed every year, not every other year.

• Make it easier to track corporate donations to candidates by requiring corporations to donate to their noncandidate committee and report it to the Campaign Spending Commission. This measure, HB 2004, would clear up a weakness in the law that led to a court ruling in Tavares v. Wong that made it more difficult for the public to track donations.

Deep-pocketed special interests will play a bigger role in political campaigns in this major election year. The public, armed with strong disclosure laws, should keep a critical and informed eye on those interests.