Hours after President Obama officially proclaimed today World Autism Awareness Day, Massachusetts Sen. Scott Brown hand-delivered a $35,545 check to the Autism Consortium in Boston.

But while the donation was coincidentally timed, Brown did not choose the charity nor did he name the amount, his Senate election rival Elizabeth Warren did.

After an oil lobbying group ran radio ads on his behalf, Brown was required to donate half the dollar amount spent on the ads to the charity of Warren's choice under the stipulations of a pledge the two signed banning funding or advertisements from outside groups in their Senate race.

"I am very pleased to donate this money to the Autism Consortium and help support their incredibly important work," Brown said in a statement. "I am also pleased that we have strengthened and expanded the People's Pledge to include issue ads."

The ad in question, which the American Petroleum Institute ran in print and radio ads, asked voters to tell Brown not to vote on a Democratic plan to eliminate subsidies for oil and gas companies. Because it did not specifically ask people to vote for Brown, it was not explicitly covered under the People's Pledge that Brown and Warren signed in January.

"Closing this loophole is an important step toward keeping outside groups from influencing the Massachusetts election," Brown said.

This is the second time Brown has paid a fine because of the pledge. In March his campaign donated $1,000 to the same autism charity after the conservative group CAPE PAC ran Google ads supporting him.

Warren has not yet had to pay a fine for violating the People's Pledge.

The two were the first national candidates to sign a pledge banning out-of-state money following the national controversy over the Citizens United Supreme Court ruling, which allows businesses and individual donors to give unlimited donations to Super PACs, which can support political campaigns but not directly coordinate with them.

Even without the groundbreaking pact, the Massachusetts senate race is expected to be one of the most closely watched races in the country. Brown and Warren are neck-and-neck in the race, one of about a dozen contests that will determine which party takes control of the Senate in 2013.

A Boston Globe survey released Sunday showed Brown, the incumbent senator, in a statistical tie with Warren, a Harvard professor best known for her consumer advocacy work in the Obama administration.

But with more than seven months until the election, the survey found that a quarter of Massachusetts voters are still undecided.

Both candidates have high favorability ratings on their own, but when respondents were asked which candidate was more likable, Brown blew Warren out of the water. Nearly 60 percent of voters said Brown was more likable than Warren, compared to the 27 percent that chose Warren as the most likable.

The Warren campaign blamed this likability deficit on the candidate's lagging name recognition. According to a December University of Massachusetts Lowell/Boston Herald poll, nearly a quarter of Massachusetts voters said they had never heard of Warren.