Outside spending by super PACs and 501(c) groups has outpaced candidate expenditures in a quarter of the Senate races this cycle, and in 17 total congressional races.

As outside spending has climbed above the numbers logged in comparable election cycles, so too has the number of races in which outside money has outpaced candidate spending. During the 2008 election cycle, outside spending exceeded candidate spending in just four races — and that’s including spending from the parties.

Of the nine Senate competitions where candidates are being outspent, five are in states where incumbent Democrats are in close fights to keep their seats: Alaska, Arkansas, Colorado, New Hampshire and North Carolina. An additional two races — Iowa and Michigan — are for seats being vacated by retiring Democrats.

The largest discrepancy between candidate and outside spending this cycle is in the Colorado Senate race between Democratic incumbent Mark Udall and Republican Rep. Cory Gardner.

Even excluding outlays by party committees, outside groups have still outspent the candidates at a rate of almost 2-1. The candidates have spent a total of $27.9 million, while outside groups have poured in $53.9. Including party spending, the ratio comes to nearly 2.5-1.

The chart below compares spending by candidates and outside groups, including party committees:

The only race to feature more outside money than Colorado is the record-setting North Carolina Senate race between incumbent Democrat Kay Hagan and Republican Thom Tillis. The more than $81 million in outside money — $56.8 million not coming from party committees — there is the most ever spent on a congressional race. Excluding the parties, outside groups have outspent the candidates by $23.6 million.

The House race with biggest discrepancy between nonparty outside spending and candidate spending is for Massachusetts’ 6th District seat. Outside groups are outspending the candidates by nearly $2 million there.

The second largest spending gap in a House race comes courtesy of Minnesota’s 8th District, which is also second on the list for overall outside spending. Outside spending is exceeding candidate expenditures $4.8 million to $3.3 million there. That faceoff, between incumbent Rep. Rick Nolan (D) and Republican Stewart Mills, is also notable because Mills holds the fundraising edge.

Including outside money from parties, the number of races in which candidates were outspent by outside groups increased from 11 to 32 from the 2010 to the 2012 cycle — and to 35 races this cycle.