As the Senate campaign committees decide where best to spend their finite resources, a battle has emerged in the state of Washington, where Republican Dino Rossi is giving Democratic Sen. Patty Murray the biggest test of her career.

The National Republican Senatorial Committee, headed by John Cornyn (Texas), initially reserved $515,000 in the state, but last week it added $2 million, Roll Call has learned. The Democratic Senatorial Campaign Committee responded by reserving $2 million Wednesday.

The $2.5 million reservation reflects the opportunity the NRSC sees in Washington against the Senate Democratic Conference Secretary, who has been in office since 1992 and has never run in an election cycle so favorable for Republicans. Rossi is a top-tier candidate and comes with higher name identification than most challengers do, having run two gubernatorial bids in the past six years.

The two Senate committees were basically even in money as of the end of July, with the DSCC reporting $22.5 million on hand and the NRSC $21.1 million.

In the next 53 days, the parties will be strategically moving money among states, with Democrats facing the more difficult prospect of determining whether or when to cut off funding in races where incumbents are involved. The NRSC is likely to follow suit behind Democrats in states where they pull money out.

So far, along with Washington, the committees have also both reserved airtime in Colorado, Kentucky and Pennsylvania. The DSCC is already on the air in Missouri, Colorado and Pennsylvania, while the NRSC has yet to run any ads. However, the NRSC has reserved time in four more states than the DSCC.

In Pennsylvania, the DSCC reserved $5.7 million, $1.5 million of which has already been spent. The NRSC has $2.5 million reserved for the open seat race between Rep. Joe Sestak (D) and former Rep. Pat Toomey (R). Toomey has led by at least 9 points in three of the previous four public polls released.

In Colorado, the NRSC has $2.3 million in advertising time reserved, and the DSCC has $4.3 million. Weld County District Attorney Ken Buck is challenging Sen. Michael Bennet (D), who was appointed to the seat last year.

The DSCC reserved $1.3 million compared with the NRSC’s $930,000 in Kentucky, an open seat race between Republican Rand Paul and Democrat Jack Conway. Two recent automated polls of likely voters found Paul ahead by 15 points, while a CNN poll of registered voters released Wednesday found the race was tied.

All of the airtime the NRSC has reserved is in October. By reserving early, the parties can save money because TV stations can raise ad rates from one week to the next.

The DSCC’s first spending priority generally is to protect the seats the party already holds. Next on the list are GOP-held open seats, of which there are several competitive ones this cycle.

Given the lowest priority in terms of spending are races that feature Republican incumbents. That’s the case in North Carolina, where the DSCC has yet to spend any money on behalf of candidate Elaine Marshall. After pumping funds into the 2008 race against then-Sen. Elizabeth Dole (R), the committee has not stepped in to assist Marshall against Sen. Richard Burr (R), who is polling in the low 40s.

With Alaska Sen. Lisa Murkowski (R) considering waging a third-party campaign, the DSCC could feel pressure to help Democratic nominee Scott McAdams, who could capitalize on Murkowski and Republican nominee Joe Miller splitting the GOP vote.

Two open seats the DSCC has yet to jump into are Ohio, where former Rep. Rob Portman (R) appears favored, and New Hampshire, which is holding its primaries next week.

However, spending in those states would force the committee out of other states where Democratic candidates could use the help. The DSCC has not reserved time in five states where the NRSC has: Florida, California, Illinois, Wisconsin and Nevada.

Four of those five states are currently held by Democrats. The NRSC has $4 million in combined coordinated and independent expenditure funds reserved in Florida, $2 million in coordinated funds in California, $3.4 million in coordinated funds in Illinois, $500,000 in Wisconsin, and $700,000 in Nevada.

The one state the DSCC has reserved time where the NRSC has not is Missouri, where Secretary of State Robin Carnahan represents one of the best chances for Democrats to pick up a GOP-held seat. In her race against Rep. Roy Blunt (R), the DSCC has already spent $1 million and has an additional $4 million reserved.

A win there would help offset expected losses in other states and increase the number of Democratic-held seats the GOP needs to take back the majority.