Minnesota Sen. Amy Klobuchar formally ended her bid for the presidency and endorsed former Vice President Joe Biden on Monday, one day before the biggest day of Democratic primary voting so far.

Ms. Klobuchar, who ran on a message of Midwestern pragmatism, took the stage with Mr. Biden at a rally in Dallas, Texas, where she paid tribute to a campaign that she said “beat the odds.” She then urged her supporters to vote for Mr. Biden in Texas and 13 other states that vote in what is known as Super Tuesday.

“We need to unite our party and our country and to do it not just with our words but our actions,” Ms. Klobuchar said. “That is why today, I am ending my campaign and endorsing Joe Biden for president.”

The rally took place several hours after aides to Ms. Klobuchar confirmed she was suspending her campaign after lackluster showings in recent early state contests. Her departure from the race came after former South Bend, Ind., Mayor Pete Buttigieg also ended his campaign. Mr. Buttigieg also endorsed Mr. Biden in Dallas on Monday.

The show of unity for Mr. Biden came as moderate Democrats are seeking to coalesce behind an alternative to front-runner Vermont Sen. Bernie Sanders.