As the larger parties charter jets and criss-cross Scotland in helicopters, SNP sources conceded its inability to compete with the financial muscle of opponents has led to a local campaign that plays on the SNP as an underdog.
The admission came as Alex Salmond issued a plea for cash from Scottish businesspeople to prop up ailing funds as polling figures suggested the Nats failed to make much impact during the first week of campaigning.
In a letter to members, he said the party needs cash to reach its target of 250,000 ahead of this week's formal campaign launch.
He wrote: "We urgently need funds. We have just three weeks to raise the final 100,000 of our election appeal. I know many of you will have already given but any additional donation will make a huge difference. I urge you to do everything you can to help."
The First Minister's plea came after previous party backer Brian Souter said he would not be bankrolling the SNP's Westminster efforts. A spokesman for the Stagecoach director, who gave the party 625,000 ahead of the 2007 Holyrood election, said he would not be donating to the party, nor would he campaign on its behalf.
Yesterday, another senior Scottish businessman said the failure of the SNP to command the large donations it did prior to the 2007 Holyrood poll showed that the party had been effectively sidelined in the UK election.
"The general election is a different election than the Holyrood vote," he said. "In this election, voters are choosing a UK government and the SNP will not be big players. People in Scotland and businessmen realise that and they will look to back one of the parties who will form the government. With the Holyrood election, businesses realised the SNP could get things done if they were in power, and they backed them.
"In this campaign, people realise that if you want to change the government, you have to back the Conservatives or Labour."
Last year individual donations fell by 10,000 to just over 160,000 and large donations were scarce, with just six of more than 10,000 during 2009.
Despite this, Mr Salmond has consistently refused to temper his claim the SNP could gain up to 20 seats in the election, allowing his party to wring a string of concessions from the larger parties in the event of a hung parliament.
Yesterday, Tory leader David Cameron poured more scorn on that notion, reaffirming comments made by William Hague in The Scotsman that the Conservatives were uninterested in negotiating with the nationalists in the event of a hung parliament.
The reduction in income, and the failure to be included in the Prime Ministerial debates has seen a change of emphasis for the SNP campaign, with the helicopter flights that marked Mr Salmond's 2007 Holyrood fight replaced by door-to-door campaigning and use of social media, viral marketing and the internet to get the party's message across.
Last week, the party had a campaign hit by parodying a Labour poster, and yesterday Mr Salmond upped his insurgency rhetoric on YouTube, telling voters that Westminster had witnessed an "extraordinary" decline since he first entered its doors 23 years ago.
At the same time, the party said Mr Salmond would tour the country in a series of "Ask Alex" meetings hosted by Elaine C Smith. The events, which appear to be designed to counter the party's exclusion from TV leaders' debates, will see Mr Salmond in Gordon, Livingston, Dundee and Glasgow, taking voters' questions.
One SNP candidate said the new tactics helped the party sell an underdog narrative to voters. "I have never seen an election where there are so many don't knows," the candidate said. "The SNP campaign is an insurgency and it may appear low key because the London parties have dominated the media, squeezing the SNP out. But this plays well on the doorstep."
But there was little evidence this approach had translated into national momentum. An analysis of the Scottish responses to the last five UK wide YouGov polls revealed the SNP virtually neck and neck with the Conservatives.
Alex Salmond's party polled 24 per cent, slightly ahead of the Tories on 23.6 per cent.