Republican businessman Mike McFadden says he has raised $700,000 in the first month of his campaign to unseat U.S. Sen. Al Franken.

McFadden announced the news in a YouTube video to supporters Tuesday, well ahead of the campaign's mid-July finance report to the Federal Election Commission.

"It's hard to believe that it's been more than a month since I filed the paperwork to run for the U.S. Senate," McFadden said in the video. "In one month, we've gained approximately 27,000 Facebook 'likes,' which my kids tell me is a good thing. I've also been humbled by the outpouring of financial support. In the first four weeks of this campaign, we've raised more than $700,000."

An executive at the Lazard finance firm, McFadden launched his Senate campaign on May 29. He faces first-term Democratic incumbent Franken, who raised nearly $2 million in the first three months of this year.

The next round of campaign finance reports, covering the months of April through June, are due to the Federal Election Commission July 15 and will contain details about who is giving to the campaign and how it is spending the money.

McFadden campaign spokesman Tom Erickson said that McFadden and his wife donated a combined $10,000 to the campaign, but that all other contributions came from outside donors.

McFadden's single month of fundraising netted almost as much money as the last Republican Senate candidate from Minnesota, Kurt Bills, raised in all of 2012. Bills scraped together $953,000 for his challenge to U.S. Sen. Amy Klobuchar, and lost by a 35-point margin. U.S. Senate races typically run in the tens of millions of dollars. In the 2008 contest between Franken and former U.S. Sen. Norm Coleman, the two raised and spent more than $40 million, for the nation's most expensive Senate race that year.

Franken, who squeaked into the seat only after a bruising election and lengthy recount, saw his approval ratings rise to 55 percent in last month's Star Tribune poll. He headed into the spring fundraising quarter with $2 million in the bank.

Political oddsmaker Nate Silver puts the Minnesota Senate race down as a "likely Democrat" win in 2014. Republicans need to capture six seats in the U.S. Senate to retake the majority.

State Rep. Jim Abeler, R-Anoka, also launched his campaign for the U.S. Senate last month. Other Republicans, including state Sen. Julianne Ortman, R-Chanhassen, reportedly also are considering a run.