DENVER -- With four months left in the race for an open Senate seat, Democratic U.S. Rep. Mark Udall is leading former Republican congressman Bob Schaffer in spending, fundraising and money left to spend.

Udall raised $2 million in the second quarter, compared to Schaffer's $1.4 million, according to reports released Tuesday. Udall also has $4 million on hand, despite outspending Schaffer $2.3 million to $775,390. Schaffer has $2.8 million.

Udall has an advantage of "a million dollars, which is real money in a Colorado race," Jennifer Duffy, an analyst who tracks Senate races for the nonpartisan Cook Political Report, told the Denver Post. "Schaffer is still at a disadvantage. It's just not as crushing as it was."

Udall spokeswoman Tara Trujillo said the results of their efforts to reach Colorado voters early in the campaign are clear. A poll conducted at the end of June, found Udall leading Schaffer 48 to 38 percent.

Schaffer campaign manager Dick Wadhams said Udall is spending more money than he is raising.

"The only thing that matters from here to the election is how much money you have in the bank, how many more bullets you have to shoot," Wadhams said.

Schaffer and Udall are vying for the U.S. Senate seat being vacated by Republican Wayne Allard.

In the 4th Congressional District race in northern and eastern Colorado, Republican incumbent Marilyn Musgrave failed to raise as much money in the second quarter as Democratic challenger Betsy Markey, who took in $389,000 to Musgrave's $280,000.

However, Musgrave still has more money left to spend than Markey. According to finance reports, Musgrave has $1.15 million, while Markey has $580,000.