Senator Chris Van Hollen of Maryland announced late Sunday night that he was recovering from “a minor stroke,” the second Democratic lawmaker to fall ill from the ailment this year.

The news highlighted the delicate balance of power in a chamber where Democrats hold a 50-50 majority and the loss of even a single vote could have momentous impact, and impede President Biden’s agenda.

Mr. Van Hollen, 63, said in a statement posted on Twitter that he had been admitted to George Washington University Hospital, which is in the District of Columbia, “after experiencing lightheadedness and acute neck pain.” An angiogram showed that he had had a “minor stroke in the form of a small venous tear” at the back of his head.

But he said that there would be “no long-term effects or damage.”

This weekend, after feeling lightheaded while delivering a speech, I sought medical attention at the recommendation of the Attending Physician. I’m feeling much better but will follow doctors' orders and curtail my schedule for the next few days. My full statement is below: pic.twitter.com/1sYq7FZMqS

— Senator Chris Van Hollen (@ChrisVanHollen) May 16, 2022

Mr. Van Hollen said that he would cut back on his schedule and remain under observation for the next few days out of an abundance of caution. He planned to return to the Senate later this week, the statement said.

In February, Senator Ben Ray Luján, 49, Democrat of New Mexico, also announced that he had had a stroke, checking himself into the hospital after experiencing dizziness and fatigue.

Carlos Sanchez, his chief of staff, said in a statement that Mr. Luján had “suffered a stroke in the cerebellum, affecting his balance.” “As part of his treatment plan, he subsequently underwent decompressive surgery to ease swelling,” the statement said.

A lawyer and progressive Democrat, Mr. Van Hollen previously served in the Maryland State Legislature before being elected to Congress in 2002. He has been a member of the Democratic House leadership, and from 2007 to 2011, he lead the Democratic Congressional Campaign Committee, which tries to help the party win and keep House seats. After his election to the Senate in 2016, he served a similar role in organizing efforts to win Senate races.

Mr. Van Hollen’s announcement about a stroke came amid the hotly contested midterm elections. Democrats have begun a fierce battle to hold onto their majority in the House and cannot afford to lose Senate seats.

Lt. Gov. John Fetterman of Pennsylvania, who is running for the state’s Democratic Senate nomination, announced on Sunday that he had suffered a stroke last Friday. “The good news is I’m feeling much better, and the doctors tell me I didn’t suffer any cognitive damage,” he said on Twitter. “I’m well on my way to a full recovery.”

Should Mr. Fetterman prevail in the primary, his rivals on the Republican side include Kathy Barnette, a hard-right conservative commentator; Dr. Mehmet Oz, a television personality and retired physician who has been backed by former President Donald J. Trump; and David McCormick, a former hedge fund manager.

Austin Ramzy contributed reporting.