President Barack Obama raised $29.1 million for his campaign and the Democratic Party in January, a strong month that added to his momentum as Republican rivals were distracted by their fight for the chance to challenge him in November.

Obama's approval ratings have been on the rise as the poor economy _ by far the most important issue in this presidential race and his biggest weakness for rivals _ continues to show signs of a recovery. He also scored a rare victory this week over congressional Republicans on taxes.

The Obama campaign announced the fundraising number in a Twitter message Friday morning. The month's haul raises Obama's total combined fundraising for this election cycle to about $250 million.

Raising money is even more important in this election after a Supreme Court ruling opened the door to big-money donations to groups that support campaigns. The so-called super political action committees are supposed to be independent of the campaigns, but critics have pointed out the possibility for abuse.

Obama often criticized the super PACs on those grounds but abruptly changed his mind and embraced them this month after their influence became clear in the Republican race. The groups already have spent millions on attack ads and are poised to spend more in the general election.

The Obama campaign did not immediately provide a breakdown of the January fundraising but said 98 percent of the donations were $250 or less. The nonpartisan Campaign Finance Institute, which analyzes contributions, found that small donors, those whose aggregate contributions amounted to less than $200, accounted for 48 percent of Obama's campaign income in 2011.

The institute found that small donors accounted for only 9 percent of 2011 fundraising for Mitt Romney, who is battling for front-runner status in the Republican presidential primary and is the party's top fundraiser.

Presidential candidates must submit January fundraising reports to the Federal Election Commission on Friday. The Obama campaign's full report was expected later in the day.

Obama was concluding a three-day swing of California and Washington that included eight fundraisers, where he was expected to raise more than $8 million.

Obama repeatedly tells his audiences that this election will be more difficult.

"And that's not going to be easy because, first of all, I'm older and I'm grayer," he told about 70 high-dollar contributors in San Francisco on Thursday night.

"And part of it is we've gone through three tough years and so people want to hope, but they've been worn down by a lot of hardship," he said _ a reference to the economy.

The Republican candidates, especially Romney, have had to focus less on the president and more on each other as the party's nominating contest stretches out longer than expected.

Romney, a former Massachusetts governor, faces an aggressive Rick Santorum, who has surged to a virtual tie in the polls after surprise wins in three states last week.

The former Pennsylvania senator on Thursday attacked Romney in the city of his birth in Michigan, challenging his values, consistency and even his economic policies. Santorum positions himself as the leading conservative in the race, while Romney has struggled to win over the party's conservative base and has been attacked for his shifting positions on sensitive issues like abortion and health care.

Romney not only grew up in Michigan, he is the son of a former governor. The state hosts a presidential primary Feb. 28, marking the end of a lull in state-by-state contests that will be followed by a 10-state Super Tuesday vote in early March.

Though Santorum and Romney are close in the polls, Romney is considered the Republican front-runner nationwide, with far more delegates from state-by-state voting that are necessary to claim the party's nomination. The multimillionaire also has far more money and campaign organization than Santorum. Romney picked up the support of Michigan Gov. Rick Snyder, who on Thursday called him "the man for the job."

The two other rivals for the Republican Party nomination _ former speaker of the U.S. House of Representatives Newt Gingrich and Texas Rep. Ron Paul _ have been relatively quiet.