Sen. Bernie Sanders' (I-Vt.) reelection campaign brought in more than $1.26 million in the first three months of 2018, according to a new filing with the Federal Election Commission.

That's more than five times what the senator raised during the same period last year, but it's less than the $1.29 million he collected in the second quarter of 2017 and the $1.95 million he raised in the third quarter of that year.

Sanders, who was first elected to the U.S. House in 1990 and the Senate in 2006, has not said whether he will seek reelection this November. No other contenders had filed reports with the FEC as of Monday afternoon.

The vast majority of Sanders' donations this year came from individual contributors, though the campaign accepted $10,000 from labor and environmental political action committees, such as the Climate Champions PAC and the National Nurses United PAC.

During the same three-month period, Sanders spent nearly $533,000. That left him, at the end of March, with nearly $6.9 million in his Senate reelection fund. But Sanders, who has declined to say whether he would mount a second presidential campaign in 2020, isn't using the money simply to stump in Vermont.

In a fundraising solicitation Sanders' reelection campaign sent supporters Monday, longtime political adviser Jeff Weaver wrote that donations to the organization would "support Bernie's effort to make Medicare for all the law of the land in this country."

"Make a $3 donation today to help us re-launch our national grassroots organizing campaign with a focus on expanding support for Medicare for all in Congress, state legislatures, and local governments all across the country," Weaver wrote. "We’re going to organize in communities everywhere, and then we are going to win."

Sanders’ fundraising this year has far outpaced that of Vermont's other two congressional delegates.

Sen. Patrick Leahy (D-Vt.), who won reelection in 2016 and doesn’t face another vote until 2022, brought in $90,438 in the first three months of the year, according to his latest FEC filing. About 44 percent of that money came from special interests, such as the Lockheed Martin Employees PAC, Bank of America Federal PAC and the Universal Music Group PAC.

Congressman Peter Welch (D-Vt.), who is up for reelection in 2018, raised $116,520 for his reelection campaign. Three-quarters of that money came from PACs, including the Petroleum Marketers Association of America, the National Community Pharmacists Association PAC and the Ironworkers Political Action League.

In an interview Monday, Welch denied that the contributions buy influence. He said his fundraising was simply an effort to be ready if an outside group attempted to fund a challenger.

"In the post-Citizens United world, the reality is that the Koch Brothers or any other billionaire can flood a campaign in a moment’s notice with secret money," Welch said, referring to the 2010 Supreme Court decision that opened the floodgates for money in politics. "I raise money in order to be prepared. And we’ve seen example after example around the country where ... secret money comes into these campaigns. It’s changed the world."

Paul Heintz contributed reporting.