PROVIDENCE, R.I. – Secretary of State Matt Brown, dogged by questions about his fundraising practices in the campaign for U.S. Senate, dropped out of the race Wednesday, citing money problems.

“I simply will not have the resources in the final stretch to run successfully,” Brown said at a news conference where he endorsed his opponent for the Democratic nomination, former Attorney General Sheldon Whitehouse, who joined him in the announcement.

They were both vying for the seat held by Republican Sen. Lincoln Chafee, who faces Cranston Mayor Stephen Laffey in the primary.

Brown had a strong showing in an independent poll by Brown University early this year, but in recent months, he has struggled with dwindling funds and persistent questions about a series of donations made to his campaign by Democratic parties in three other states.

Brown in March acknowledged he asked several of his most generous donors to contribute money to state Democratic parties in Hawaii, Maine and Massachusetts after those parties gave him a total of $25,000. Watchdogs and political opponents accused him of trying to circumvent campaign finance laws that limit the amount of money individuals can give to campaigns.

The Republican parties in Hawaii and Rhode Island sent a complaint to the Federal Elections Commission asking for an investigation. Brown denied wrongdoing, but returned the money.

According to quarterly FEC reports filed this month, Brown had just $35,000 left in his campaign coffers for the primary, while Whitehouse had more than $1.3 million.

Mary Diamond, executive director of the Rhode Island Republican Party, said Brown’s announcement was not a surprise.

“People thought that Matt Brown was out before today,” she said.

She said she did not know what would happen to the party’s FEC complaint against him.

Brown said he would have to keep raising money to retire his campaign debt, which totaled $173,000 at the end of the first quarter. He said he would also work to raise money for Whitehouse.

Brown, who was a community activist before he was Secretary of State, said he would not file to run for re-election.

Several other candidates are running to replace him in the November election.