In a political environment that has tilted heavily in favor of Republicans, the Democratic Senatorial Campaign Committee is employing its limited coordinated expenditures earlier than its GOP counterpart.

This year, the DSCC spent $1.8 million in coordinated expenditures, or funds spent in consultation with preferred candidates, through May 31, with just less than $1 million spent in May.

The National Republican Senatorial Committee, meanwhile, doled out just under $29,000 in coordinated expenditures, with about $16,000 going to boost now-Sen. Scott Brown, who won a January special election in Massachusetts, and about $13,000 for North Dakota Gov. John Hoeven, who is a lock to become the next Senator from that state.

In the world of campaign spending, the most important difference between coordinated expenditures and independent expenditures is that the former has limits based on state population while the latter is unlimited — so long as the committees do not collaborate with the candidate.

Independent expenditures inevitably dwarf coordinated expenditures in any given election cycle and end up having a much greater effect on the outcome of campaigns.

In the 2008 cycle, the DSCC spent $3.8 million on coordinated expenditures and $72.6 million on independent expenditures, while the NRSC spend $1.5 million on coordinated expenditures and just under $39 million on independent expenditures.

But coordinated expenditures can also serve an important purpose.

“In Senate races, coordinated expenditures are almost always on TV,” GOP direct-mail consultant Dan Hazelwood said. Hazelwood said coordinated dollars can be crucial, especially early on.

Coordinated expenditures “usually buy at least a week of [TV] time and allow campaigns to plug a gap in their ability to run their advertising,” Hazelwood said.

Another bonus of coordinated expenditures is that they give the campaign committees the ability to buy TV time at a cheaper rate than independent expenditures do.

In two cases so far this cycle, the DSCC spent coordinated funds on candidates who won’t be in the general election.

In Pennsylvania, the DSCC spent more than $1.2 million on Sen. Arlen Specter’s losing bid for the Democratic nomination. In the Keystone State, the coordinated expenditure limit this cycle is just more than $1.7 million, meaning Rep. Joe Sestak, who beat Specter, can now only count on about $500,000 in coordinated funds from the national party for the rest of the cycle.

In North Carolina, the DSCC spent $193,000 to help former state Sen. Cal Cunningham’s failed primary campaign. That means the committee has that much less to spend on coordinated expenditures for Secretary of State Elaine Marshall, who won the Democratic nomination. The coordinated limit in North Carolina is just over $1.2 million.

Another place where the DSCC made significant use of its coordinated expenditures during the primary was Arkansas, where the committee spent more than $242,000 helping Sen. Blanche Lincoln get through her tough challenge.

In Colorado, the DSCC dropped more than $71,000 on coordinated expenditures for appointed Sen. Michael Bennet, who faces a stiff primary challenge from former state Speaker Andrew Romanoff. Romanoff earned the backing of former President Bill Clinton this week.

The committee also spent smaller amounts on coordinated expenditures in several states, including New Hampshire, where it is aiding Rep. Paul Hodes; Florida, to help Rep. Kendrick Meek; and Nevada, for Senate Majority Leader Harry Reid.

On the House side, the Democratic Congressional Campaign Committee has spent $130,000 on coordinated expenditures this cycle while the National Republican Congressional Committee has not spent any coordinated funds.