Yes We Can Video: https://www.youtube.com/watch?v=1yq0tMYPDJQ&list=RD1yq0tMYPDJQ#t=44

DNC and RNC

Raise funds to, in part, support the spread of the message

They also help to prepare the country to receive the message by spreading the party agenda well before the race.

Case in point, "50 state strategy"

Howard Dean pursued an explicit Democratic "50-State Strategy" as chairman of the Democratic National Committee, putting resources into building a Democratic Party presence even where Democrats had been thought unlikely to win federal positions, in hopes that getting Democrats elected to local and state positions, and increasing awareness of Democrats in previously conceded areas, would result in growing successes in future elections. Democrats who supported the strategy have said that abandoning red states as lost causes only allowed the Republican Party to grow even stronger in areas where it was unchallenged, resulting in lopsided losses for Democrats in even more races.[2]

During the 2008 United States presidential election, Barack Obama attempted a form of the fifty-state strategy to reach into deep red states to try to flip them. This was largely based on Obama's appeal during the primaries in very Republican states, like the Deep South, and the Great Plains states.[3] In September, Obama scaled back his fifty-state strategy, abandoning Alaska and North Dakota and reducing staff in Georgia and Montana. John McCain's choice of Sarah Palin as his running mate made winning Alaska very unlikely for Obama, and she also had strong support in North Dakota.[4] Obama was ultimately able to win Virginia and Indiana, two states that had not voted Democratic since 1964, and North Carolina, last won by a Democrat in 1976.