WASHINGTON (CNN) -- Arizona Sen. John McCain voted at least three times Thursday in the Senate after missing more than a month of votes to campaign for a presidential bid.

Prior to today's votes, McCain's missed about half of the Senate's scheduled votes so far this year, which is far more than the five other Senators running for president according to the Congressional Quartely, which monitors Congress. Senators Sam Brownback, R-Kansas, and Joe Biden, D-Delaware, each missed about 30 percent of the votes this year. Connecticut Sen. Chris Dodd missed about 20 percent. At the low end, New York Sen. Hillary Clinton and Illinois Sen. Barack Obama, each of which barely missed any votes this year.

The only Senator to miss more votes than McCain is Sen. Tim Johnson, who's recovering from a brain hemorrhage he suffered in December.

So what gives? McCain's playing catch up to rivals Mitt Romney and Rudy Giuliani in the crucial battle for campaign cash and because of that, his campaign says the Senator has increased his fundraising time around the country, giving McCain an even larger platform to talk about the issues he cares about. But that means missing out on votes, a job he was elected to do.

McCain's office said he hasn't missed any votes where it would have come down to him. He told CNN's Ted Barrett that he will make every effort to get back for a vote if he's the deciding factor. "I have assured the leadership I'll do everything I can," McCain said.

On the campaign trail in Oklahoma Monday, McCain said that "the people of Arizona understand why I'm missing the votes."

The Arizona senator is expected to vote this evening in favor of the Iraq supplemental spending bill.

McCain also isn't the first Senator to spend more time out on the trail than back on the Hill. Sen. Joe Lieberman, Sen. John Edwards and Sen. John Kerry also missed a lot of votes the last time around.