In the first sign that Democrats are preparing to pull out the party’s big financial guns for US Senate nominee Edward J. Markey, Michelle Obama is scheduled to appear at a Boston fund-raiser for the Malden congressman later this month, an event that can collect up to $37,600 from an individual donor.

The First Lady, who is making her first fund-raising appearance since the November presidential election, will headline the party at the Taj Boston on May 29, according to a copy of the invitation that has been sent out to the party’s big donors.

“The White House has made it clear it will do anything the Markey campaign wants of it,’’ said one senior Democratic leader who is raising funds for the congressman’s senatorial race.

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That person said that President Obama, too, is likely to make an appearance in Massachusetts for Markey before the June 25 election if the campaign requests his help. Markey, a 36-year veteran of the US House, is facing Gabriel E. Gomez, a Cohasset businessman and former Navy SEAL who, in a major upset, captured the GOP nomination in his first attempt in a statewide race.

The Democrats currently control the Senate on a 55 to 45 margin, with two independents caucusing with the Democrats.

Michelle Obama last made a fund-raising appearance in Massachusetts when she headlined an event in June 2011 at a private Newton residence to raise money for her husband’s reelection.

The May 29 fund-raiser is the first major event sponsored by Markey Senate Victory, a joint fund-raising committee created two weeks ago by the Markey Committee and the Democratic Senatorial Campaign Committee. Senators Elizabeth Warren and William “Mo” Cowan are listed as the other two hosts. The minimum contribution for the event is $500.

Joint committees between a candidates’ committee and a national party have become increasingly common fund-raising entities because they can accept donations of up to $37,600 under federal campaign finance statutes. The money is allocated between the national party and the candidate’s campaign according to the terms of the agreement that sets up the joint committee.

The DSCC, in an unusual move, endorsed Markey at the outset of the campaign in late December as state and Washington Democrats looked to avoid a primary fight in the special election to fill the seat vacated by John F. Kerry. US Representative Stephen F. Lynch, a South Boston Democrat, did not back off, launching his campaign soon afterward. Markey won the primary election on Tuesday, 58 to 43 percent.