A hung Parliament at Westminster would provide Scotland with the "greatest opportunity", First Minister Alex Salmond has said.
Mr Salmond said the prospect of no one party winning an overall Commons majority was now a "probability".
He argued that, in those circumstances, the SNP - who have set the target of winning 20 seats in the May 6 election - could seek to extract gains for Scotland.
Mr Salmond, also the SNP leader, spoke out at the launch of his party's election manifesto in Glasgow.
It sets out a number of areas where Nationalist MPs would seek to make gains - by, for example, pressing for Holyrood to have greater financial powers.
SNP leaders also want Scotland to be included in the first phase of any future high-speed rail line.
Mr Salmond said the travel chaos caused by the cloud of volcanic ash highlighted the need for this, stating: "As the events of recent days have shown, the Scottish economy cannot rely on domestic air travel alone."
He declared: "A vote for the SNP is a vote for maximising the influence for Scotland."
The party has also been arguing that more SNP MPs could help protect Scotland from the brunt of future spending cuts.
Mr Salmond said: "More Nats will mean less cuts and it means that the things that matter most to the people of Scotland can be protected."