President Obama’s reelection campaign will begin accepting donations sent by text messages this week, marking the first foray into a potentially lucrative new avenue of grass-roots fundraising for federal candidates.

The program, announced by campaign officials early Thursday, will allow supporters to send contributions of less than $50 by texting “GIVE” to 62262 — which corresponds with the letters in “Obama.”

Officials said the service will be available almost immediately for Verizon, Sprint, T-Mobile and U.S. Cellular customers, and for AT&T and other carriers “in the near future.” Possibilities include soliciting text donations in broadcast and Internet ads and during major political events, such as the upcoming Democratic Party convention in Charlotte, N.C.

“Accepting small donations by text message will help us engage even more grassroots supporters who want to play a role by donating whatever they can afford to the campaign,” campaign manager Jim Messina said in a statement.

The move into text message donations, which copies a fundraising tactic long used by the American Red Cross and other charities, follows a series of decisions by the Federal Election Commission allowing the practice under protocols that adhere to campaign laws. Lawyers for both Obama and Republican challenger Mitt Romney had urged the FEC to approve the strategy.

Under the system, which was first proposed by two attorneys at the Arent Fox law firm, text message contributors will see their donations charged to their wireless bill and would be limited to less than $50 in contributions per month and $200 total during an election cycle.

Technically speaking, each text would actually be a pledge purchased by a third-party aggregator and then sold to the campaign for a fee. The arrangement is aimed at complying with FEC rules that require any political donation to be deposited within 10 days — an impossible standard for text contributions tied to monthly cellphone bills.

It’s unclear how much the wireless carriers and third-party processors will charge campaigns for collecting text donations. Such fees can eat up as much as half of the total in some commercial transactions, but the FEC ruled that political campaigns can negotiate discounted rates without running afoul of contribution rules. An Obama official said the campaign will “pay the most competitive rates available in the marketplace to ensure our supporters have the greatest impact with their contribution,” but declined to provide details.

The push to approve text donations was backed by a bipartisan array of interest groups, including campaign-finance watchdogs who view it as a potential counterweight to monied donors. The cellphone industry initially balked over liability concerns, but the FEC said earlier this month that the campaigns and companies working with them would bear responsibility for ensuring that donors were U.S. citizens or legal permanent residents and complying with contribution limits.

Obama’s campaign has long pursued donations by sending text messages with links to Internet donation pages, but that required donors to enter credit card information through a Web page. Experts say clearing away that obstacle could open the floodgates to a new source of funds for political campaigns, since nearly 10 percent of Americans have already made charitable donations via text message.

Brett Kappel, a Democratic campaign finance attorney at Arent Fox who helped bring the initial proposal to the FEC this year, called text donations a “Big Bang” that will “expand the political universe exponentially” for campaigns at all levels.

The strategy could prove particularly important for Obama, whose campaign focuses heavily on small-dollar donors and has fallen badly behind Romney in fundraising in recent months.

As an example of what to expect, the campaign said video screens at upcoming events could include a plea for cellphone funds that reads: “To contribute $10 to Obama for America, text GIVE to 62262.”

The Romney campaign said it also will start accepting donations by text message soon, but declined to provide details.