Campaign donations pay for more than political ads and should not be protected as free speech, former Supreme Court Justice John Paul Stevens told a Senate panel Wednesday in urging them to rein in the billions of dollars shaping elections.

The retired justice reminded lawmakers that political donations funded the burglary at the Watergate office complex under President Richard Nixon. That break-in at the Democratic National Committee is not speech, Stevens argued in a rare appearance of a former justice in the Senate.

“While money is used to finance speech, money is not speech. Speech is only one of the activities that are financed by campaign contributions and expenditures. Those financial activities should not receive precisely the same constitutional protections as speech itself,” Stevens said. “After all, campaign funds were used to finance the Watergate burglary, actions that clearly were not protected by the First Amendment.”

Stevens has been a critic of his former colleagues’ decisions that have opened the floodgates for unlimited donations and super PACs.

At issue are the millions of dollars that influence elections — if not determine their outcome — with various degrees of openness. Recent Supreme Court rulings have permitted individuals and corporations to write unlimited checks to independent political committees, while other groups can accept cash and disclose the donors’ identities months or years later, if ever.

“These tactics have no apparent purpose other than to conceal the sources of funds,” Federal Election Commission vice chairwoman Ann Ravel said.

Ravel was not testifying in her FEC role but in her capacity as a former chair of the California Fair Political Practices Commission, the state’s version of the FEC that leveled a record $1 million fine against the Center to Protect Patient Rights and Americans for Responsible Leadership. Their recipient, the Small Business Action Committee PAC, also had to return millions of dollars in donations from those groups.

Democrats have criticized the new rules and those who take advantage of them, including some of their allies. Republicans, meanwhile, have embraced the system and used the rules to power well-funded groups such as Americans for Prosperity.

That group operates under rules that allow it to keep donors’ identities secret, unlike those who give to groups like the Republican National Committee. The conservative billionaire brothers Charles and David Koch have backed Americans for Prosperity with millions, but understanding their impact in real time is impossible because they technically do not operate as political groups.

“Our democracy is at risk. That’s the problem here,” said Sen. Chuck Schumer, the New York Democrat who chairs the Senate Rules Committee that hosted the hearing.

But Republicans did not share that concern, especially as it relates to the Koch brothers.

“Let’s stop demonizing citizens who exercise their First Amendment rights,” said Sen. Pat Roberts of Kansas, the top Republican on the panel. “The First Amendment does not allow us to silence those who oppose us.

Countered Democratic Sen. Tom Udall of New Mexico: “Money and speech are the same thing? This is tortured logic.”

Schumer said the Senate this year would schedule a vote on Udall’s proposed constitutional amendment that would limit federal candidates’ ability to raise and spend money. The measure also would regulate and limit the ability of super PACs to impact elections.

Changes to the Constitution are difficult and the vote was more political than practical. The vote, however, would force Republicans to either defend unlimited money in campaigns or put them in the awkward position of condemning their allies.

Wednesday’s Senate Rules Committee hearing was the first since the Supreme Court’s ruling that lifted limits on how much total money individual donors can give to candidates. The court left in place a limit on how much individual candidates can take from each donor, but the justices cleared the way for donors to give the maximum amount to every candidate on the grounds that restrictions limit free speech rights.

Campaign donations pay for ads, of course. But that money also pays for polling, operatives’ salaries and offices — the nuts and bolts of a campaign operation that aren’t necessarily speech.

The Karl Rove-supported American Crossroads super PAC raised almost $5.2 million last month from three organizations and 21 individuals. The average donation was more than $218,000. The largest donation — $2 million — came from former Univision owner Jerry Perenchio. A trust tied to Oklahoma coal executive Joseph Craft III gave $500,000, as did Arkansas-based investment manager Warren Stephens and Kentucky-based self-storage mogul B. Wayne Hughes.

Fred Eychaner, the founder of Chicago-based Newsweb Corp., wrote a $4 million check to the Senate Majority PAC, a Democratic group with ties to Senate Majority Leader Harry Reid. The group raised $11 million during the first three months of the year, including $2 million from James Simons, founder and chairman of investment firm Renaissance Technologies.